In 1974, when I was at Stirling University, the Python team set up camp in the area to film Monty Python And The Holy Grail. The show was huge at the time: student TV lounges were packed when it was on. The production team contacted the university to find extras; as a member of the drama group, I was very keen. I was told to turn up one morning at a hall in town where I would be fitted with a costume and given a role.

I was going to be a peasant, but when another chap was too short to fit into John Cleese’s Sir Lancelot the Brave costume (to be his stand-in while John played the role of Tim the Enchanter), we swapped parts. I’m 6ft 2in. There was only one costume as the film was shot on a shoestring. (They famously used coconuts to mimic hooves because they couldn’t afford real horses.)

We filmed this scene in a disused quarry near the Duke’s Pass in the Trossachs. We set off in a minibus about 8am: me, Eric Idle, Michael Palin, Terry Jones, a couple of crew and two extras. Graham Chapman was sitting in the front, drinking a can of lager. He was struggling with his drinking at the time. They were all hungover; they’d been in a pub the night before, and Graham had scandalously kissed every man at the bar and been kicked out. I was 20, a decade or so younger than them.

John’s character was a wizard who emitted explosions from his hands and a staff; pipes carrying the gas were laid across the paths. I wore a helmet over my face and had to be careful where I walked. That was the only downside of taking John’s place – nobody can see my face. He starts the scene standing on a pinnacle, with a sheer drop either side. He was up there for nearly an hour, and it was pretty windy. The team kept shouting: “Are you all right?” The extent of my acting involved pretending my imaginary horse was rearing when the bangs went off.

There was a lot of sitting around in our knitted chainmail, waiting for the light to improve. But I was awestruck. I spent most of the day with Eric, Michael and Graham, doing the Guardian crossword. There were some surreal conversations. One concerned how the Pythons would survive if they were stranded in the jungle after a plane crash: who would make the best hunter, hut-builder – but the overriding dilemma was who they’d eat first if they ran out of food.

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My other scene was the last one of the film; I played one of the policemen who bundle the knights into a van. The last shot features me, standing behind another policeman who puts his hand over the camera, turning the screen black. Local kids who’d come to watch flicked me the V sign, thinking I was a real copper.

The following year, I went to see the film in Edinburgh in a double bill with Woody Allen’s Manhattan. I loved it, and was thrilled my scenes hadn’t been cut. Seeing myself standing with the Pythons still gives me a kick.

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