“NO-ONE ever told me there was so much potassium in a banana,” recalls Tony Benn, to much amusement, as he records his final diary entry.

Though the man himself has been dead for five years and wasn’t prone to recording his innermost thoughts in front of a live audience, this engaging and immersive theatrical conceit, the brainchild of director Andy Barrett and director Giles Croft and based on Benn’s diaries, sees Philip Bretherton don a dressing gown, spark up a pipe and embark upon a remarkable performance as the formidable parliamentarian.

The challenges are obvious. Bretherton is over 20 years Benn’s junior, doesn’t immediately resemble the Labour Party stalwart and has to deliver a monologue, complete with those mellifluous intonations and Bennite mannerisms, for over an hour.