What sound does a screaming foetus make? It’s not the kind of question that most theatre plays provoke you to ask, but Mike Bartlett’s new piece about climate change is not a normal play. At the end of the first half of this rollercoasting epic, dazzlingly directed by Enron maestro Rupert Goold and which opened last night, the image of a foetus crying out in the womb seems perfectly reasonable. It’s that kind of show; fuelled by a wildly imaginative vision, when it ignites it burns like phosphorous. And, believe me, that changes your perceptions.

Everybody in the business says don’t think Sondheim is easy. I’ve seen galas where big names stumbled in under-rehearsed numbers, and last night Bryn Terfel and Maria Friedman slipped and almost fell on the same banana skins that had done for them in a hastily semi-staged Sweeney Todd. Not enough to matter, though, and they rightly brought the house down. And the show as a whole?

It's very hard to ever know what to expect from Alan Moore, the Mage of Northampton. The author of era-defining comics like Watchmen, V For Vendetta and From Hell has long maintained that art and magic are one and the same, and since the mid-1990s his works have often tended to be long and complex explications of various occult principles, which while eye-opening can often lose readers in all their baroque unfoldings.

With summer now fully upon us, and tourists flocking to the West End, it seems a good time to lift the bonnet on the tireless engine of London’s long-running hit shows. Over the next six weeks theartsdesk will be giving six of London’s hardest-working and longest-running classics – Les Miserables, The Lion King, Chicago, Billy Elliot, The Woman in Black, and of course The Phantom of the Opera – the once-over, checking to see whether all really is still running as smoothly and efficiently as it once was.

Never have the Tudors seemed so real. After decades of TV and film characters keeping us at a teasing, ermined distance, Hilary Mantel's dazzling novel Wolf Hall brings it all to life as never before, and the Globe's still-running Henry VIII has vigorously built on that. But the Stuarts?

This, Heinrich von Kleist’s last play, was completed not long before he committed suicide, aged 34, in 1811, when the map of Europe - and indeed that of his native Prussia - was changing with indecent frequency. It is loosely (very loosely) based on the real Prince of Homburg and events at the Battle of Fehrbellin in 1675, and with its leitmotif of honour, duty and loyalty to the Fatherland, it is no wonder that the play was appropriated (with suitable adjustments) by the National Socialists in the 1930s (it was a favourite of Hitler's apparently) and then fell out of favour in German theatre in the postwar period.

What makes a good piece of theatre? Is it the atmosphere generated? Is it the acting? Or is it the ability to communicate ideas clearly? I don’t mind if sometimes I can’t hear or understand words. In the past, I have been overwhelmed by Polish versions of Dostoyevsky’s The Idiot. I have watched open-mouthed at Kabuki without surtitles and when Federico Garcia Lorca’s Yerma was first seen in this country, in Peter Daubeny’s World Theatre seasons, back in the Sixties, you hardly needed to understand Spanish to be so desperately moved by the sense of yearning emanating from a production played out on a giant trampoline that looked like an enormous cat’s cradle. Lorca, it turns out, is the chosen author for a new production that has its own issues.

If you could boil down Robert Tressell’s brilliant socialist novel to a single observation, it would be that rich people do nothing, while the poor work their (ragged-trousered) arses off. So it’s a very clever conceit on the part of Howard Brenton’s new adaptation for the Chichester Festival, as well as a thrifty move for what must be one of its lower-budget productions, to have members of the workforce play their well-to-do exploiters. They line up near the beginning as if queuing for stewed tea or tools, and instead receive padded waistcoats and rubbery facemasks, all tusk-like moustaches and flushed pink cheeks. It’s like the metamorphic end of Animal Farm going into reverse.

The longest and most densely historical play by Georg Büchner (1813-37) is a potential monster. In German, Dantons Tod can run to four hours or more. There's little action and much speechifying. In plays by his equally wordy, history-obsessed predecessor, Friedrich von Schiller, there are at least fights, battles, a lot of love - and some sex.

The Martin McDonagh phenomenon is a curious one. He burst upon the world in 1996, aged 26, born in Camberwell, the son of Irish parents. The quirk of fate that placed him in south east London may or may not have been the making of him. But by pure accident, and whether he actually knew the people involved or not, it aligned him with what was to become the abiding zeitgeist of the mid-Nineties: BritArt and Damien Hirst and Tracey Emin.