Du Goudron et Des Plumes, Barbican/ Flogging a Dead Horse, Roundhouse Studio

Five people stand in the dark. A bleak gantry descends with a rumble onto their heads. They scuttle under it and flatten themselves to escape a crushing, but then they get up and start building. The platform is stripped of planks, rebuilt at crazy angles, refashioned while decorating the tasks with acrobatic surprises.

At a steep tilt a plank is both a slide and human catapult, or makes a terrific wobbling noise if slapped right; as an upright it’s perfect for a girl to shin up and then array herself in a bouffant Boucher Pompadour dress of crumpled paper, later to be elegantly torn off in strips while she swings on a white rope trapeze.

Its inventiveness has that happy freedom where the performers have such an inquiry about their skills that they invented themselves right out of old rules. It's acrobatics dancing, exploring the edge of gravity, full of fantasy and pleasure. The ephemerality of the set in this first part, planks slipping with a crash, gleeful springs on temporary seesaws that you feel sure will splinter the wood, teetering gambols on the edge of falling, heedless aerial swinging around cables, all gradually travels on with creaks, clangs and rumbles to something more like a sea adventure. The raft (which continues to evolve as holes appear, trapdoors snap open, chunks disappear) now starts to swing rhythmically, and its hollow middle allows some brilliantly adroit tricks of swapping places - it's like people trying get off a lurching boat onto the jetty and vice versa, constantly ending up in the wrong place, and so deftly done that my sides hurt with laughter.

Then the raft rises to become an upper floor, and with Gallic clown humour and physical expertise you see a man upright, with his mirror image, a man upside down, his feet, vase of flowers and bottle of water all exactly mirroring the upright ones, and then his attempts to keep this Down Under world in complete synch with the upper one - the concept coming adrift when he opens his water bottle... Oh dear, this is not a show to describe, it is one to enjoy.

Yes, it ends three times when one would be enough (the Titanic tilt would do it for me - stunning), and there are a couple of overlong solos, which I assume are to allow the incredibly hardworking troupe an occasional breather. But Du Goudron et des plumes inhabits a highly individualised outer space between circus skills, mime and contemporary dance with enormous fun and awesome brilliance. Soundscore, lighting, set and performers flow together in a highly imaginative theatricality and the standing ovation was justified. Four nights isn’t enough - this show has to return.

Meanwhile, one night with Faulty Optic is quite enough, thank you. This British duo have wildly acclamatory press for previous shows with their puppets, old faces with pointy noises and sticky-out ears, and a gruesome attitude. Flogging a Dead Horse, given its “world premiere” last night at the Roundhouse Studio Theatre, is supposed to have the joke on us by not being a puppet show but a two-man sketch-comedy about two negligibly interesting nerds in their attic, one listening to radio signals, the other chopping up brains and making Rorshach blots with brain gunge and black sauce.

They question each other incessantly about what they think this sounds like, or that looks like. This continues for half an hour. One of them gives us a lecture on film of neurons that apparently thinks it is clever and amusing. Later, they do drag on a few puppets, none of them manipulated with any intrigue, a “dead” horse puppet that won’t stand up (hence the title), a stuffed body that can be either a woman (in a spangly belly-dancing bikini, hoho) or an old man, and both can be desultorily violated.

Talking is a serious miscalculation here. The dramaturgy of mad scientists with some fairly weird sex fantasies, and some deep-sea life thrown in, is dreadfully thin and spotty; possibly that achingly long first half with the questions about what you see is intended to set you up for seeing what you make of the second part. But frankly the text is so dumb and the puppetry so underwhelming that I could understand easily why there were several walk-outs during the show (in such a small venue, it was a sizeable dent). Given that its soundtrack was its best feature, the idea would have been far more effective if, in fact, Faulty Optic had done it in mime.

• Du Goudron et des plumes is at the Barbican Theatre, London till tomorrow
• Flogging a Dead Horse is at the Roundhouse Studio Theatre, London till Sunday (sold out)
  
• London International Mime Festival website for all shows (ends Sunday)