‘Rupert was an exciting actor. He would just do things’ … Everett and Kenneth Branagh in the 1982 West End transfer of Another Country. Photograph: Alastair Muir  In 1979, when Mrs Thatcher stood up in the Commons and announced that the third man in the Burgess and Maclean spy case was Anthony Blunt, lots of people wrote articles and books saying how easy it must have been for these men to go over to Russia. But their reasoning didn't explain it to me. There's a great difference between betraying your country and wanting to change the world.  What wasn't really mentioned was that almost all the men involved were gay – though I'm not sure we said "gay" back then – and had all been to the same kind of public school. I'd been at Winchester myself. Though I hadn't been rebellious, I knew the oppressive way boarding school can work on people, and probably still does.  Another Country, which came more easily than anything I'd ever done, was set in a 1930s public school and looked at how such places might turn people into traitors. I wrote it in six weeks but nobody would put it on as it had no star parts. I think everyone was frightened by the subject matter: treason and homosexuality. The National and the Royal Court both rejected it.  So I sent it to Alan Strachan who was running Greenwich theatre. He'd directed a play of mine with Alec Guinness and said: "OK Julian, but get the money from someone else." I went to Barclays on the corner of Markham Square off the Kings Road and asked for a loan – the manager was a sculptor in his spare time and was known to be sympathetic to the arts.  Greenwich was a good place to start a play. Our director Stuart Burge had run the Royal Court but was nervous about Another Country. He'd been so miserable at his own public school that the play was painful to him. But he was one of the few people who could manage Rupert Everett, who was playing the lead, Guy Bennett. There was a lot of fooling around on stage. I caught Rupert at it once, being unprofessional in an afternoon matinee – making things up as he went along. I gave him the most enormous rollicking. I certainly wasn't a father figure to him though, Rupert had a daddy of his own.  When we transferred to the West End, people's expectations had been whetted by the Greenwich reviews and in the end we ran for 19 months – a very long time for a straight play. Some people came again and again, dressed in blazers and boaters and reading aloud from copies of the script. There was even a clothes shop in the West End called Another Country. Nobody offered me a straw hat. I would have quite liked one.  Things aren't like they were. The way the country has been sold to the Chinese and the Russians – these are things that wouldn't have been approved by public-school boys. Yet it's the public school boys who have done them.  Rupert was an amazing success: there was a real sense of "a star is born". I joined the production after it transferred. It was my first part, and I was worried my working-class background was a problem. There were a number of playwrights I just could not do: Noël Coward and that high style, which required a confidence I believed to be the product of a certain education, a social ease, a way of being.  At auditions, Rada told us to dress for the part – don't make them use their imaginations. So I hit upon the idea that men like this would wear striped blazers. I turned up at Julian's house and he said: "You're wearing the jacket. Ah, you must get the part!" I'd been rumbled.  I was living with my then girlfriend in a tiny bedsit. I first read the script in the launderette. Bloody hell! I was shocked. Underneath all this fun and insight into public school life was a serious look at a generation of intellectuals funnelled into a system where something had to give. I rang my agent in disbelief: "This is going into the West End? We're kids. Do they know what they're doing?"  Rupert was an exciting actor. He would just do things. When they were dramatic, they were brilliant – they took the play to another level. Sometimes, they were funny: one day, my bed had been filled with shaving cream. Another time, out of nowhere, Rupert walked on wearing a kilt. I thought: "Jesus Christ! Julian is in this afternoon. We are going to be dead." I was in Rupert's dressing room when Julian came in, incandescent. I saw for the first time the meaning of steam coming out of someone's ears.  I remember the end of our run with fondness. Rupert and I were amazed we had lasted six months. I said: "Do you want to see the understudies take over? One is called Daniel Day-Lewis, another guy is called Colin Firth."  • Guardian Extra ticket offer available here
Writer Julian Mitchell and actor Kenneth Branagh remember the struggle to mount a risky anti-establishment play, and how Rupert Everett did his best to spice it up