A doddery waiter has just somersaulted backwards down the stairwell.
Indeed, the spindle-shanked Alfie is sent flying on a regular basis by James Corden's Francis, the roly-poly bungler at the centre of One Man, Two Guvnors. Thankfully, in this realm of brilliantly executed slapstick, the oldster proves shatterproof. He totters back up the stairs for further mayhem, this time with a slopping great tureen of soup.
In Richard Bean's new farce – an instant National Theatre hit, freely adapted from Carlo Goldoni's The Servant of Two Masters (1753) – Francis is juggling two jobs in Brighton, 1963. He's been hired as the flunky of a ludicrous toff called Stanley and as a minder for a gangster named Roscoe. However, being a pea-brained fool with an insatiable appetite, he gets into a frightful pickle. He even absentmindedly scoffs letters that he's supposed to deliver post-haste to Stanley. Or was it Roscoe? Gulp.
With Cal McCrystal credited as associate director, Nicholas Hytner's production is terrifically bouncy and often howlingly funny. Its zany acrobatics gives the dust-encrusted genre of commedia dell'arte a vigorous new lease of life, even as designer Mark Thompson embraces retro stylishness, with Sixties beehive hairdos, and the seaside town painted on canvas flats as in pantomime.
Cordon is having a ball, zipping to and fro in a cops'n'mobsters chase, and beating himself up for being an idiot – a one-man brawl. The cast's teasing rapport and interactions with the audience add to the vibrancy. Not only does a skiffle band perform for us between scenes. Cordon drafts in sidekicks from the stalls, hauling them up on stage.
Bean and Hytner have been more obviously polemical before, not least in England People Very Nice, in 2009, which sent up British xenophobia using un-PC racial stereotypes. But they're surely testing the boundaries of comedy here, too. Once or twice, I was crying with laughter which turned to unease as the onstage violence (including one stalls "volunteer") escalated wildly. You might wonder, fleetingly, if you're part of some mass psychology test, a variant on the notorious Milgram experiment of 1963 in which participants, with alarmingly little empathy, persisted in pressing an electric-shock button while hearing screams.
However, there's no harm done, really, in One Man, Two Guvnors. It's enormous fun, with a hilarious supporting performance from Oliver Chris as the punch-slinging, public-school twit, Stanley.
What nice pronouncement can one make, though, about Pygmalion starring Rupert Everett as Henry Higgins, the phonetics professor who, in a reckless experiment, determines to pass off a cockney flower girl as a duchess? The best one can say is that Philip Prowse's production is so dismally unfunny that George Bernard Shaw's arguments about class mobility come through loud and clear, unadulterated by wit.
Still, Lord love a duck, Everett is awful. A charm-free zone, he sits scowling in what looks like Edwardian villain make-up, woodenly facing downstage or rotating 90 degrees to continue glaring, in profile, at the proscenium arch. He barely deigns to glance at Eliza (the pretty-as-a-picture non-star, Kara Tointon) and her aperçu that Higgins is "all bounce and go" seems like a bad joke.
For those who prefer to be off the leash, the great outdoors last week became a stunning setting in Fissure, devised by Louise Ann Wilson (formerly of wilson and wilson). Her sister Denise, died of a brain tumour in 2001, aged 29. Ten years on, this three-day walk through the Yorkshire Dales – where the siblings grew up – was a kind of loving pilgrimage, a journey through memory and mourning, as well as a pleasantly sociable hike.
Fissure also poetically maps a personal tragedy on the landscape, letting it merge with ancient myths (Greek and Christian) about lingering spirits, underworlds and death-defying ascensions that, in the end, offer solace.
Silent dancers, haunting folk singers (their harmonies scored by Jocelyn Pook), and scientific experts materialised, as if by magic, en route as 70 or so hardcore promenaders trekked over spectacular terrain led by Wilson and mountain guides. The singer Olivia Chaney, with an exquisite natural purity, warmth and heartfelt intensity, is surely a star in the making.
The mini-lectures – delivered by (real-life) Professor Michael Brada of the Royal Marsden and Dr Chris Clark of UCL's Institute of Child Health – were not only medically illuminating. Describing tumours and how neuro-imaging uses water to trace the brain's pathways, their talks also fascinatingly echoed Day One's surrounding vistas of cracked and undulating limestone – eerily resembling magnified grey matter – and the dripping subterranean caverns of Day Two.
This was not performance art for the timid. Choreographed by Nigel Stewart, young female dancers poignantly embodied the dying and the heartbroken sibling respectively, rolling down slopes, emerging from underground streams, squeezing through narrow crevices and pot-holing between locations. Day Three verged on the seriously dangerous, when crosswinds of around 50mph blasted us, 500 metres up on Ingleborough Peak. Clinging to boulders, I asked myself whether a theatre critic being literally blown away by a show could be considered an artistic triumph. Unforgettable.
'One Man, Two Guvnors' (020-7452 3000) to 26 July. 'Pygmalion' (0844 412 4662) to 3 September
Kate Bassett sees David Tennant and Catherine Tate lock horns in a West End Much Ado About Nothing
Rupert Goold's bold Merchant of Venice, at Stratford's RST (to 26 Sep), is set in a fantasy-tinged Las Vegas, where Portia and her casket-guessing suitors star in a TV game show. Edward Albee's A Delicate Balance is satirically surreal, too, at London's Almeida, with Penelope Wilton as the pushy American wife (to 2 Jul).