If the Trocks didn't exist, we would have to invent them. Every genre needs its loving parodists, treading the fine line between homage and dommage, and an art form as stylised and convention-governed as classical dance is riper for it than most - as evidenced by the continuing worldwide success of this all-male comedy troupe after more than 40 years.

Sure as carbon dioxide and the greenhouse effect, the 2010s are following a standard 20-year nostalgia cycle by embracing the 1990s as their "retro twin" decade. The quiet rumblings of the last few years – student Nineties parties and the reappearance of the crop top – have this year flowered into a full-on revival that has hairdressers fingering their razors (remember the Rachel cut?), thirty-somethings wearing double denim again, and Rambert coming to Sadler’s Wells with revivals from 1990-1 alongside a Merce Cunningham classic from the Nineties’ own retro twin decade, the 1970s.

Rambert is making a thing of acquiring classic works from the 20th-century contemporary repertory – and a very good thing, too. First staged by them last year, RainForest, a minor Merce Cunningham piece from 1968, was recently performed by the Cunningham company itself, in London on its final tour. And yet, while that performance was straight from the horse’s mouth, I think Rambert (whisper it) in reality do it better.

Time is a rare privilege in a choreographer’s career - in Britain, anyway. We don’t have the equivalents of Merce Cunningham, Martha Graham or Paul Taylor, who build careers into their eighties and beyond, with mighty efforts from private patrons and friendly art giants of their generation (Andy Warhol, Robert Rauschenberg, Isamu Noguchi et al). UK choreographers are fortunate to get 10 years until the Arts Council deems it time to push them out of the subsidised nest, to vanish in their late thirties, most of them.

I wasn’t around to see when Karole Armitage won her spurs in her twenties as a punk ballet choreographer in America in the 1970s and early Eighties, so we must rely on her programme-sheet biography to explain to us that she is “seen by some critics as the true choreographic heir" to George Balanchine and Merce Cunningham. After last night’s dismal showing by her group, Armitage Gone! Dance, at the Southbank Centre, the only possible response is, “Pull the other one” and a firm slap across the hubris.

Any newcomers to Merce Cunningham who visit the last performances ever in Britain of his modern dance company - renowned, even notorious, for its abstruse abstractness - will surely go away with an impression of laughter, playfulness, the lightness of being. On two more nights, tonight and tomorrow, this landmark company will perform his dances, and then - like the end of his piece Ocean, which you can see on film tomorrow - when the clock runs out, the last dancer will leave the stage, and that will be the end of it.

Dance is eating itself. Or dancers are eating themselves, rather. It's on-trend to defy the idea of the mute dancer, and instead have them verbally explaining themselves, their motivation, their art. This year’s Dance Umbrella launched last night with the “self-contemplation” of Cédric Andrieux, a handsome blond Frenchman, who regales us in a charming murmur for 80 minutes with the story of his career, with danced illustrations.

Tonight the company dedicated to the greatest radical of modern dance, Merce Cunningham, opens its farewell tour to London, a valedictory odyssey that will end next year. Last year Cunningham died, aged 90. He had just premiered a work called Nearly Ninety, and this is fittingly the last thing we will see of his company as it blazes one final circuit before closing down in December 2011.