Christopher And His Kind explores Isherwood’s formative years in 1930s Berlin in the run-up to the Second World War and airs at 9.30pm on Saturday on BBC Two.

Director Geoffrey Sax (Doctor Who: ‘The Movie‘, Stormbreaker) told CultBox: “He learned how to do Isherwood’s walk and the voice. We then let it go a bit as we didn’t want him to be hamstrung with it. He was so immersed in the character and watched so many hours of footage; he spoke like him a lot, even off camera. Not all the time, but he’d always start the voice well before a shot so by the time we said action he was already there.”

He also commented: “Matt was very, very focused; very prepared. When we first met, just after I’d been brought on board, he and I went for coffee together and he’d already done a huge amount of research. I was going to encourage him to do that, but he’d already done it!”