The reason is the world première of Gulliver's Travels, Romanian wunderkind Silviu Purcarete's latest epic reimagining of classic literature. Outside the theatre, the building's doors are flanked either side by two life-size cut-outs of cartoon knights in shining armour, with large holes where their faces should be, enabling passers-by to put their heads through. The effect is of a seaside pier sideshow, made even more so by the pair of extravagantly frocked damsels drumming up trade for photo opportunities beside them.
While at first glance this stunt might look like a conceptual gag to accompany Purcarete's production, which opens this week as part of Edinburgh International Festival's theatre programme, on closer scrutiny it becomes clear that all this is an elaborately staged ad for a well-known brand of cleaning fluid, the manufacturers of which are sponsoring the show.
On a wall at the side of the theatre, the contradictory relationship between art and commerce is made even more explicit via a series of crudely pasted-up posters of satirical slogan-adorned drawings.
'Culture is Good/Crisis Culture Is Good' reads one atop a picture of two figures, one displaying his two empty trouser pockets, the other sporting a crown and presumably playing the king for all he's worth.
Onstage, several young women dressed in jodhpurs and bridles whinny and clip-clop their way about a hay-strewn stage, impersonating horses.
Later, giant rats rut for all they're worth. A row of bowler-hatted men in suits and carrying umbrellas and brief-cases waddle on like penguins, lining up before a little boy on a wooden rocking horse who watches much of the action unfold around him while a deep baritone voice narrates a tale that appears to reference the global recession and capitalism in crisis during one man's journey around a strange world.
There are some recognisably Purcarete style dramatic tics and tricks in what is more a theatrical collage than a play, staged, unlike his mammoth version of Faust that promenaded its audience through Edinburgh's Royal Highland Centre in EIF 2009, in a regular proscenium arch theatre. This barely contains Purcarete's ideas made flesh by a large-scale ensemble cast, who include Ofelia Popii, who played Mephistopheles so fearlessly in Faust.
What isn't familiar are all the received notions of what Jonathan Swift's 19th century satire actually contains. There is no Lilliput, and there are no little people pinning down a giant Gulliver, images familiar from the numerous big-screen adaptations of the book, the most recent of which came in 2010, featuring Jack Black as Gulliver. With the action punctuated throughout by Irish composer Shaun Davey's score, Purcarete has concentrated instead on the little-know fourth part of the novel, A Voyage to the Country of the Houyhnhnms, which features horses as the perfection of nature, while human beings are debased creatures known as Yahoos. All of this is demonstrated via the sort of coup de theatre only Purcarete can get away with, albeit one which it would be quite wrong to reveal here.
Beyond the show's politics, there is some Irish-looking slapstick that more resembles something by Samuel Beckett than Purcarete's other work. It is too clearly a personal Gulliver's Travels. The little boy onstage may represent a young Gulliver, who in turn becomes the embodiment of Swift, but there is much of Purcarete in him too. In Sibiu, at least, it was Purcarete's voice providing the narration, while the simple pleasures the boy finds through playing with his toys recalls the sledge treasured by a young Charles Foster Kane in Orson Welles' seminal feature film, Citizen Kane. Unlike Welles' epic, Purcarete's Gulliver's Travels is seen through a child's eye view throughout.
The morning after the premiere, Purcarete sits in the office of Sibiu International Theatre Festival director, Constantin Chiriac, who founded festival 19 years ago, and has developed it into one of the largest theatre festivals in the world. If Chiriac is the embodiment of east European largesse, Purcarete is a shy, modest figure. While not without a dry wit, he prefers to let his work onstage do his talking for him.
"From the beginning it was clear we were not going to do a full dramatisation of the novel," he mutters through his beard.
"That would be impossible. The initial proposal was that we should make a poetic performance inspired by the book, and mainly from the fourth book, which nobody knows. Even in our country, there is a short version of Gulliver's Travels for children, which everybody knows, and nobody knows anything else. The message of this show is please go and read this book."
It wasn't Purcarete's idea to tackle Gulliver's Travels. The initial proposal came from partners in Ireland and Edinburgh as a direct result of the response to Faust.
While Purcarete appears to shrug off any international pressures, he's happy to admit that audience reaction closer to home is more of a concern.
"We were more scared here," he says, as the festival goes on beyond the theatre office. "Most of the people here come to see Gulliver and the dwarfs. They come to see the story of their childhood which they know through Gulliver, and think they may become shocked and angry by what they see, and will forget the fact that they never read this book. But it is not only from the fourth book. We use parts from the other books, like the cannibalism of children, and the poem about prostitutes in Drury Lane. We have a fragment of his epitaph, and it's more about Jonathan Swift than it is about Gulliver."
Outside the theatre below, rain has given way to lunchtime sunshine, which has brought Sibiu's incoming theatre-goers onto the streets. The brightly-frocked damsels are still touting for trade to get their picture taken posing as knights with the sponsors' hoardings. Around the corner, the makeshift anti-capitalist fly-posters flap about in the breeze.
Upstairs, Purcarete is musing on life beyond Gulliver's Travels. There are rumours that Purcarete will be tackling another Irishman's even more fantastical novel in the form of Ulysses, by James Joyce. It is, however, a rumour he's keen to play down.
"This is a legend for the future," he says. "For now, let's just think about Gulliver."
Gulliver's Travels is at Edinburgh's King's Theatre from tonight to Monday. www.eif.co.uk