Was it Bobby Charlton who said football is a game of two halves? Probably. Anyway, as far as I am aware no-one has so far observed that improvisational comedy is. Which is odd, because Dead Man In A Box’s performance at the Liberties theatre, Camden, was exactly that.

Before the interval their improvisation - while undeniably sharp, well-oiled and impressive - failed somewhat to find the funny bone. After it, with a little more structure and perhaps a little more on their own territory, they frequently unearthed genuine, laugh-out-loud moments.

The six performers worked off cues from the audience to create a Big Brother-style reality TV show (called, improbably, Nelson Mandela’s Zoo of Rage). Flirting, bantering and fighting quite convincingly as the dimwitted, emotionally volatile contestants, their best moments came through surreal interaction with the animal inmates of the zoo. Especial mention goes to the man who spent almost the entire first act locked apparently in coitus with a polar bear.

A nice touch was that Nelson himself - as the omniscient Big Brother of the piece - was played by whoever happened not to be involved in the scene each time, and the differing interpretations of his accent made him sound like, variously, a reasonable approximation of the great man himself, a Danish person, and, (memorably) an odd cross between a campy version of Yoda and an eight-year-old Bangladeshi boy.

However, at times the first act did drag. The various characters of the contestants were either insufficiently different or over-the-top caricatures, and once or twice the performers succumbed to the temptation - which must be strong - simply to go surreal for the sake of it, rather than with a joke in mind.

It should be said, in fairness, that most of the audience seemed to disagree with me on this - they loved it - but to hell with them; I’m the reviewer, so I know best.

The inspired substitution at half-time (if I am allowed to resurrect the football comparison) was swapping the standard show format for Nelson Mandela’s Celebrity Zoo of Rage.

Kris Akabusi, Fred Dibnah, J K Rowling, Moses, Billy Idol and Marie Antoinette may not instantly spring to mind as obvious housemates, but, paradoxically, by forcing the performers to pick more definite characters it gave them better scope for jokes.

Some fantastic set-pieces (Harry Potter’s multi-millionaire creator manually pleasuring a pig was particularly good, although I could have done without the lingering mental image) were matched by some brilliant spur-of-the-moment visual gags - Moses in the hot-tub, parting the waters to retrieve the soap, was inspired.

Another favourite was the weirdly touching love affair between Akabusi and Dibnah (“D’tha like traction engines?” “Awooga.”), which included an elegantly timed cut-away by the Geordie narrator (“Two hours later, past anything controversial”) when the two of them strayed on to the subject of race.

Meandering through Rowling’s frankly disturbing attempt to breed a hippogriff by spit-roasting a badger, and ending in an unexpected bloodbath, the second act had everything the first lacked.

To return one last weary time to the rapidly cooling corpse of the football metaphor, if the first half was Arsenal - technically impressive and easy on the eye, but with no end product - the second was more Liverpool circa 1977. Back of the net

Tom Chivers