Walton was sent to a local school, but in 1912 his father saw a newspaper advertisement for probationer choristers at Christ Church Cathedral School in Oxford and applied for William to be admitted. The boy and his mother missed their intended train from Manchester to Oxford because Walton’s father had spent the money for the fare in a local public house. Louisa Walton had to borrow the fares from a greengrocer. Although they arrived in Oxford after the entrance trials were over, Mrs Walton successfully pleaded for her son to be heard, and he was accepted.

At Oxford Walton befriended several poets including Roy Campbell, Siegfried Sassoon and, most importantly for his future, Sacheverell Sitwell. Walton was sent down from Oxford in 1920 without a degree or any firm plans. Sitwell invited him to lodge in London with him and his literary brother and sister, Osbert and Edith. Walton took up residence in the attic of their house in Chelsea, later recalling, “I went for a few weeks and stayed about fifteen years”.

The Sitwells looked after their protégé both materially and culturally, giving him not only a home but a stimulating cultural education. He took music lessons with Ernest Ansermet, Ferruccio Busoni and Edward J. Dent. He attended the Russian ballet, met Stravinsky and Gershwin, heard the Savoy Orpheans at the Savoy Hotel and wrote an experimental string quartet heavily influenced by the Second Viennese School that was performed at a festival of new music at Salzburg in 1923. Alban Berg heard the performance and was impressed enough to take Walton to meet Arnold Schoenberg, Berg’s teacher and the founder of the Second Viennese School.

In 1923, in collaboration with Edith Sitwell, Walton had his first great success, though at first it was a succès de scandale. Façade was first performed in public at the Aeolian Hall, London, on 12 June. The work consisted of Edith’s verses, which she recited through a megaphone from behind a screen, while Walton conducted an ensemble of six players in his accompanying music. The press was generally condemnatory. Walton’s biographer Michael Kennedy cites as typical a contemporary headline: “Drivel That They Paid to Hear”. The Daily Express loathed the work, but admitted that it was naggingly memorable. The Manchester Guardian wrote of “relentless cacophony”. The Observer condemned the verses and dismissed Walton’s music as “harmless”. In The Illustrated London News, Dent was much more appreciative: “The audience was at first inclined to treat the whole thing as an absurd joke, but there is always a surprisingly serious element in Miss Sitwell’s poetry and Mr Walton’s music … which soon induced the audience to listen with breathless attention.” In The Sunday Times, Ernest Newman said of Walton, “as a musical joker he is a jewel of the first water”.

Walton was a slow worker. Both during composition and afterwards he would continually revise his music; he said, “Without an india-rubber I was absolutely sunk.” Consequently, his total body of work from his sixty-year career as a composer is not large. Between the first performance of Façade in 1923, for example, and that of the Sinfonia Concertante in 1928, he averaged only one small piece a year. Of his work as a whole, Byron Adams in Grove’s Dictionary of Music and Musicians writes:

Walton’s works of the 1920s, while he was living in the Sitwells’ attic, include the overture Portsmouth Point, dedicated to Sassoon and inspired by the well-known painting of the same name by Thomas Rowlandson. It was first heard as an entr’acte at a performance in Diaghilev’s 1926 ballet season, where The Times complained, “It is a little difficult to make much of new music when it is heard through the hum of conversation.” Sir Henry Wood programmed the work at the Proms the following year, where it made more of an impression. The composer conducted this performance; he did not enjoy conducting, but he had firm views on how his works should be interpreted, and orchestral players appreciated his “easy nonchalance” and “complete absence of fuss.” Walton’s other works of the 1920s included a short orchestral piece, Siesta (1926) and a Sinfonia Concertante for piano and orchestra (1928), which was well received at its premiere at a Royal Philharmonic Society concert, but has not entered the regular repertory.

From the days of 78 rpm discs, when relatively little modern music was being put on record, Walton was favoured by the record companies. In 1929 the small, new Decca company recorded eleven movements from Façade, with the composer conducting a chamber ensemble, with the speakers Edith Sitwell and Walton’s friend and colleague Constant Lambert. In the 1930s, Walton also had two of his major orchestral works on disc, both on Decca, the First Symphony recorded by Harty and the London Symphony Orchestra, and the Viola Concerto with Frederick Riddle and the LSO conducted by the composer. In the 1940s Walton moved from Decca to its older, larger rival, EMI. The EMI producer Walter Legge arranged a series of recordings of Walton’s major works and many minor ones over the next twenty years; a rival composer expressed the view that if Walton had an attack of flatulence (he used an earthier expression), Walter Legge would record it.

The Viola Concerto (1929) brought Walton to the forefront of British classical music. It was written at the suggestion of Sir Thomas Beecham for the viola virtuoso Lionel Tertis. When Tertis received the manuscript, he rejected it immediately. The composer and violist Paul Hindemith stepped into the breach and gave the first performance. The work was greeted with enthusiasm. In The Manchester Guardian, Eric Blom wrote, “This young composer is a born genius” and said that it was tempting to call the concerto the best thing in recent music of any nationality. Tertis soon changed his mind and took the work up. A performance by him at a Three Choirs Festival concert in Worcester in 1932 was the only occasion on which Walton met Elgar, whom he greatly admired. Elgar did not share the general enthusiasm for Walton’s concerto.

Elgar having died in 1934, the authorities turned to Walton to compose a march in the Elgarian tradition for the coronation of George VI in 1937. His Crown Imperial was an immediate success with the public, but disappointed those of Walton’s admirers who thought of him as an avant garde composer. Among Walton’s other works from this decade are more film scores, including the first of his incidental music for Shakespeare adaptations, As You Like It (1936); a short ballet for a West End revue (1936); and a choral piece, In Honour of the City of London (1937). His most important work of the 1930s, alongside the symphony, was the Violin Concerto (1939), commissioned by Jascha Heifetz. The concerto, Walton later revealed, expressed his love for Alice Wimborne. Its strong romantic style caused some critics to label it retrogressive, and Walton said in a newspaper interview, “Today’s white hope is tomorrow’s black sheep. These days it is very sad for a composer to grow old … I seriously advise all sensitive composers to die at the age of 37. I know: I’ve gone through the first halcyon period and am just about ripe for my critical damnation.”

Between 1934 and 1969 he wrote the music for 13 films. He arranged the Spitfire Prelude and Fugue from his own score for The First of the Few (1942). He allowed suites to be arranged from his Shakespeare filmscores of the 1940s and 1950s; in these films, he mixed Elizabethan pastiche with wholly characteristic Waltonian music. Kennedy singles out for praise the Agincourt battle sequence in Henry V, where the music makes the charge of the French knights “fearsomely real.” Despite Walton’s view that film music is ineffective when performed out of context, suites from several more of his filmscores have been assembled since his death.

Walton’s first major composition after Belshazzar’s Feast was his First Symphony. It was not written to a commission, and Walton worked slowly on the score from late 1931 until he completed it in 1935. He had composed the first three of the four movements by the end of 1933 and promised the premiere to the conductor Hamilton Harty. Walton then found himself unable to complete the work. The end of his affair with Imma von Doernberg coincided with, and may have contributed to, a sudden and persistent writer’s block. Harty persuaded Walton to let him perform the three existing movements, which he premiered in December 1934 with the London Symphony Orchestra. During 1934 Walton interrupted work on the symphony to compose his first film music, for Paul Czinner’s Escape Me Never (1934), for which he was paid £300.

After a break of eight months, Walton resumed work on the symphony and completed it in 1935. Harty and the BBC Symphony Orchestra gave the premiere of the completed piece in November of that year. The symphony aroused international interest. The leading continental conductors Wilhelm Furtwängler and Willem Mengelberg sent for copies of the score, the Chicago Symphony Orchestra premiered the work in the US under Harty, Eugene Ormandy and the Philadelphia Orchestra gave the New York premiere, and the young George Szell conducted the symphony in Australia.

Walton’s house in London was destroyed by German bombing in May 1941, after which he spent much of his time at Alice Wimborne’s family house at Ashby St Ledgers in the countryside of Northamptonshire in the middle of England. While there, Walton worked on projects that had been in his mind for some time. In 1939 he had been planning a substantial chamber work, a string quartet, but he set it aside while composing his wartime film scores. In early 1945 he turned again to the quartet. Walton was conscious that Britten, with Les Illuminations (1940), the Sinfonia da Requiem (1942), and Peter Grimes in 1945, had produced a series of substantial works, while Walton had produced no major composition since the Violin Concerto in 1939. Among English critics and audiences, the Violin Concerto was not at first rated one of Walton’s finest works. Because Heifetz had bought the exclusive rights to play the concerto for two years, it was not heard in Britain until 1941. The London premiere, with a less famous soloist, and in the unflattering acoustics of the Royal Albert Hall, did not immediately reveal the work as a masterpiece. The String Quartet in A minor, premiered in May 1947, was Walton’s most substantial work of the 1940s. Kennedy calls it one of his finest achievements and “a sure sign that he had thrown off the trammels of his cinema style and rediscovered his true voice.”

In 1944, it was said of Walton that he summed up the recent past of English music and augured its future. Later writers have concluded that Walton had little influence on the next generation of composers. In his later years, Walton formed friendships with younger composers including Hans Werner Henze and Malcolm Arnold, but although he admired their work, he did not influence their compositional styles. Throughout his life, Walton held no posts at music conservatoires; he had no pupils, gave no lectures and wrote no essays. After his death, the Walton Trust, inspired by Susana Walton, has run arts education projects, promoted British music and held annual summer masterclasses on Ischia for gifted young musicians.

In 1947, Walton was presented with the Royal Philharmonic Society’s Gold Medal. In the same year he accepted an invitation from the BBC to compose his first opera. He decided to base it on Chaucer’s Troilus and Criseyde, but his preliminary work came to a halt in April 1948 when Alice Wimborne died. To take Walton’s mind off his grief, the music publisher Leslie Boosey persuaded him to be a British delegate to a conference on copyright in Buenos Aires later that year. While there, Walton met Susana Gil Passo (1926–2010), daughter of an Argentine lawyer. At 22 she was 24 years younger than Walton (Alice Wimborne had been 22 years his senior), and at first she ridiculed his romantic interest in her. He persisted, and she eventually accepted his proposal of marriage. The wedding was held in Buenos Aires in December 1948. From the start of their marriage, the couple spent half the year on the Italian island of Ischia, and by the mid-1950s they lived there permanently.

In the 1930s, Walton’s relationship with the Sitwells became less close. He had love affairs and new friendships that drew him out of their orbit. His first long affair was with Imma von Doernberg, the young widow of a German baron. She and Walton met in the late 1920s and they were together until 1934, when she left him. His later affair with Alice, Viscountess Wimborne (born 1880), which lasted from 1934 until her death in April 1948, caused a wider breach between Walton and the Sitwells, as she disliked them as much as they disliked her. By the 1930s, Walton was earning enough from composing to allow him financial independence for the first time. A legacy from a musical benefactress in 1931 further enhanced his finances, and in 1934 he left the Sitwells’ house and bought a house in Belgravia.

Walton’s last work of the 1940s was his music for Olivier’s film of Hamlet (1948). After that, he focused his attentions on his opera Troilus and Cressida. On the advice of the BBC, he invited Christopher Hassall to write the libretto. This did not help Walton’s relations with the Sitwells, each of whom thought he or she should have been asked to be his librettist. Work continued slowly over the next few years, with many breaks while Walton turned to other things. In 1950 he and Heifetz recorded the Violin Concerto for EMI. In 1951 Walton was knighted. In the same year, he prepared an authorised version of Façade, which had undergone many revisions since its premiere. In 1953, following the accession of Elizabeth II he was again called on to write a coronation march, Orb and Sceptre; he was also commissioned to write a choral setting of the Te Deum for the occasion.

Troilus and Cressida was presented at Covent Garden on 3 December 1954. Its preparation was dogged by misfortunes. Olivier, originally scheduled to direct it, backed out, as did Henry Moore who had agreed to design the production; Elisabeth Schwarzkopf, for whom the role of Cressida had been written, refused to perform it; her replacement, Magda László, had difficulty mastering the English words; and Sargent, the conductor, “did not seem well acquainted with the score”. The premiere had a friendly reception, but there was a general feeling that Hassall and Walton had written an old-fashioned opera in an outmoded tradition. The piece was subsequently staged in San Francisco, New York and Milan during the next year, but failed to make a positive impression, and did not enter the regular operatic repertory.

In 1956 Walton sold his London house and took up full-time residence on Ischia. He built a hilltop house at Forio and called it La Mortella. Susana Walton created a magnificent garden there. Walton’s other works of the 1950s include the music for a fourth Shakespeare film, Olivier’s Richard III, and the Cello Concerto (1956), written for Gregor Piatigorsky, who gave the premiere in January 1957 with the Boston Symphony Orchestra and the conductor Charles Munch. Some critics felt that the concerto was old-fashioned; Peter Heyworth wrote that there was little in the work that would have startled an audience in the year the Titanic met its iceberg (1912). It has nevertheless entered the regular repertoire, performed by Paul Tortelier, Yo-Yo Ma, Lynn Harrell and Pierre Fournier among others.

Apart from an early experiment in atonalism in his String Quartet (1919–22), which he later described as “full of undigested Bartók and Schoenberg”, Walton’s major essays in chamber music are his String Quartet in A Minor (1945–46) and the Sonata for Violin and Piano (1947–49). In the opinion of Adams in Grove’s Dictionary, the quartet is one of Walton’s supreme achievements. Earlier critics did not always share this view. In 1956 The Record Guide said, “[T]he material is not first class and the composition as a whole seems laboured.”

In 1966 Walton successfully underwent surgery for lung cancer. Until then he had been an inveterate pipe-smoker, but after the operation he never smoked again. While he was convalescing, he worked on a one-act comic opera, The Bear, which was premiered at Britten’s Aldeburgh Festival, in June 1966, and enthusiastically received. Walton had become so used to being written off by music critics that he felt “there must be something wrong when the worms turned on some praise.” Walton received the Order of Merit in 1967, the fourth composer to be so honoured, after Elgar, Vaughan Williams and Britten.

Walton’s orchestral works of the 1960s include his Second Symphony (1960), Variations on a Theme by Hindemith (1963), Capriccio burlesco (1968), and Improvisations on an Impromptu of Benjamin Britten (1969). His song cycles from this period were composed for Peter Pears (Anon. in Love, 1960) and Schwarzkopf (A Song for the Lord Mayor’s Table, 1962). He was commissioned to compose a score for the 1969 film Battle of Britain, but the film company rejected most of his score, replacing it with music by Ron Goodwin. A concert suite of Walton’s score was published and recorded after Walton’s death. After his experience over Battle of Britain, Walton declared that he would write no more film music, but he was persuaded by Olivier to compose the score for a film of Chekhov’s Three Sisters in 1969.

Of his ballets for Sadler’s Wells, The Wise Virgins (1940) is an arrangement of eight extracts from choral and instrumental music by Bach. The Quest (1943), written in great haste, is, according to Grove, oddly reminiscent of Vaughan Williams. Neither of these works established itself in the regular repertoire, unlike the ballet score Walton arranged from the music of Façade, the music for which was expanded for full orchestra, still retaining the jazz influences and the iconoclastic wit of the original. Music from The Quest and the whole of the Viola Concerto were used for another Sadler’s Wells ballet, O.W., in 1972.

Walton revised the score of Troilus and Cressida, and the opera was staged at Covent Garden in 1976. Once again it was plagued by misfortune while in preparation. Walton was in poor health; Previn, who was to conduct, also fell ill; and the tenor chosen for Troilus pulled out. As in 1954, the critics were generally tepid. Some of Walton’s final artistic endeavours were in collaboration with the film-maker Tony Palmer. Walton took part in Palmer’s profile of him, At the Haunted End of the Day, in 1981, and in 1982 Walton and his wife played the cameo roles of King Frederick Augustus and Queen Maria of Saxony in Palmer’s nine-hour film Wagner.

Walton died at La Mortella on 8 March 1983, at the age of 80. His ashes were buried on Ischia, and a memorial service was held at Westminster Abbey, where a commemorative stone to Walton was unveiled near those to Elgar, Vaughan Williams and Britten.

Almost all Walton’s works have been recorded for commercial release. EMI published a “Walton Edition” of his major works on CD in the 1990s, and the recording of the Chandos Records “Walton Edition” of his works was completed in 2010. His best-known works have been recorded by performers from many countries. Among the frequently recorded are Belshazzar’s Feast, the Viola and Violin Concertos and the First Symphony, which has had more than twenty recordings since Harty’s 1936 set.