The Belgian play Gardenia, the subject of a poignant documentary Before the Last Curtain Falls, opens with a series of tableaus in which trans performers and drag queens between the ages of 60 and 70 strip from their suits. 

“It is literally about people’s layers; the clothing, the makeup, the voice, the movement,” says German filmmaker Thomas Wallner, who captures the stories behind the false eyelashes and raised eyebrows. “But that is just a reflection of what is going on the inside; trying to make the inner identity conform to the world at large.”

Coinciding with Kardashian patriarch and former Olympian Caitlyn Jenner’s debut on the cover of Vanity Fair, and Madame Tussauds’ plans to make Laverne Cox the first ever transgender wax figure, Wallner’s timely documentary about the art performance (whose triumphant run took in over 200 performances in 25 countries over two years) explores gender-reassignment surgery and the experience of being part of the post-war LGBT generation.

"Gardenia had emboldened [the cast] – in some cases set them free,” says the director, whose film is a meditation on childlessness, ageing, and the past experiences of those in the cast who have endured "prostitution to pay for all the sex change operations.” "Danilo [Povolo] never revealed he had worked as a prostitute, and even more unbelievably, Rudy [Suwyns] never revealed he was gay. But through Gardenia, Rudy managed to out himself to a select few people. To the rest of the world he was an actor."

Before The Last Curtain Falls plays at Open City Documentary Festival, London, June 16-21.