I was in a restaurant with my best friend at the time, Terence Stamp, and Harry Saltzman came into the restaurant and sat at another table — he was very famous for producing the Bonds with Cubby Broccoli. He sat down with his family and then he saw me and sent a note over with the waiter: “Would you have coffee with me at the end (of the evening)?” So I obviously said yes, and then later I sat down with him, and he asked me whether I knew a book by Len Deighton called The Ipcress File. I said that I did and that I was half-way through it. He then asked me if I liked it and I replied that I thought it was great. Then he asked, “Would you like to play the lead in it?” and of course I replied, “Yeah, that would be great.”

Then we had to figure out a name for the lead character. Harry said that the spy was dull and boring and that we should think of a boring name, and I suggested Harry, and immediately apologised because of who I was talking to. But he said it was all right because his real name was Herschel, and so we decided on Harry. Then I remembered I had been at school with someone called Palmer, who was the most boring boy I’d met. So that was it, we settled on Harry Palmer.

We decided we wanted him to be the antithesis of Bond. Obviously he wasn’t any great competition for Bond, he was not a suave spy. He was more like a real spy; an ordinary guy, who you wouldn’t look twice at in the street. We gave him some glasses. I wore glasses and so knew how to use them; but what worked for me was that as soon as I took my glasses off, I wasn’t Harry Palmer.

On the first day of shooting I was on my way and the driver said to me: “Are you in this film, The Ipcress File?” I said I was and he responded that the book was “the biggest load of crap” he’d ever read. Then when we got there, Sidney Furie, the director, came to me and said: “I’ll tell you what I think of this script, have you got any matches?” and he burnt the script on the floor of the studio at Pinewood. This was meant to be the start of my big-time movie career and nobody liked the script.

I remember once we were filming in Notting Hill, in Lionel Blair’s flat, and Sid (Furie) had a row with Harry. Sid started to cry and ran off set. He got on the No 12 bus and Harry and I had to chase him in a Rolls-Royce Phantom down Bayswater Road. We kept coming alongside the bus shouting, “Stop, our director’s on board,” and the bus driver would go “Screw you.” Anyway, we got him back and it all went very well in the end.

The Ipcress File was very important for me. The first review I read was “Well, here we have 003 and a half,” but then there was an extraordinarily good review and I knew that I had a career in movies playing leading characters, if not the star role. I was 31 and for the first time in my life I knew I had a future in this business after being an actor for 11 years. I remember that I started to cry, and I crumpled up the review and I threw it out of the window as a way of saying: “Well, I’m on my way now,” and I never looked back.

This interview is included as an extra on The Ipcress File: Special Edition DVD, out to buy from Monday. The film is on selected cinema re-release. The Michael Caine season runs at the National Film Theatre, London SE1 (www.bfi.org.uk/incinemas/nft), until Jan 31