In 2012, she played the lead role in Vivienne Franzmann's second play The Witness, at the Royal Court Theatre. She received rave reviews with Susannah Clapp from The Observer stating, "Always thought Pippa Bennett-Warner had big future. Now she is having it in ‘The Witness’ at Royal Court...There are actresses (even actors) who are more flashy, who more obviously inflect every detail of a speech. PBW is completely natural. Audiences of course admire her: but they do something else, which is not always the same thing: they believe her”. Bennett-Warner went on to secure a nomination for Best Actress at the Evening Standard Theatre Awards 2012, alongside Cate Blanchett and Dame Eileen Atkins and was named as one of the 1000 Most Influential Londoners in 2012 in the category "Generation Next" by The Evening Standard.