This was very much a case of simply no one knowing what was going to happen next, neither performers nor audience.

For stand-up comic, Have I Got News For You panellist (for 32 years!) travel presenter and comedy historian Paul Merton was back improvising with his merry band – and causing comedy chaos.

Here the experienced team, including Richard Vranch, Mike McShane, Merton’s wife Suki Webster and accompanist Kirsty Newton were continuing an age-old theme, particularly memorable from late-1980s TV show Whose Line Is it Anyway?

This evening, the last night of a 50-date tour which began in March, they were joined by comedian/actress Ruth Bratt (speciality corpsing) who slotted in seamlessly.

Each show is unique, with the audience suggesting themes, sketches, locations, voices and more, with the Chums acting them out, often with hilarious consequences.

It takes skill and guts to work without the safety net of a script, but that’s what makes this all the more interesting. These Chums could probably improvise in their sleep, such is their expertise, and their teamwork is extraordinary.

Their wit and speed of thought is extraordinary as they live on the edge through scenes such as Mary Poppins and a potato masher, a naked rollercoaster ride or the Great Catsby.

It’s incredibly clever stuff, keeps the audience marvelling at the wonder of it, smiling constantly and occasionally guffawing uncontrollably at the comedy anarchy of the proceedings.

Merton is the ringmaster keeping things chugging along and very much in charge but content to let the others shine. The American McShane – now 66 and seemingly moving with difficulty – shines out and Vranch quietly and effectively goes about his business.

Webster and Bratt combined beautifully for musical numbers, of which there were many, with the multi-talented Newton brilliant, but mostly underutilised, on the keyboards. Webster and McShane stole the show, though, with their film noir, Les Mis and Rocky Horror musical takes on life on a cruise ship.

It is, of course, an age-old format but to witness expert practitioners at the height of their game was a joy, particularly when Merton had to guess a fiendishly difficult occupation – something like the operator of a ventriloquist of a Joan of Arc dummy, dressed in armour in the Vatican on Shrove Tuesday – from cryptic clues suggested by the others.

They finished with a version of Shakespeare – The Comedy of Horrors, as suggested by someone in the crowd – which was so good I harboured thoughts (wash my mouth out) that some passages had been planned and then slotted into whatever play they were pastiching.

In any case, two hours flew by and I could have done with a third.