Revelations: The time: 1973 The place: The Gate cinema, Notting Hill, London The man: Steven Isserlis, cellist
It must have been when I was about 13 or 14. I went to see a Marx Brothers film: The Cocoanuts (1929), their first one. I remember thinking, when Harpo and Chico first appeared, "what extraordinary people". I was a bit nonplussed. But by the end of the film I had become a total and utter obsessive.

I had become a fan, but it went further. The character of Harpo Marx almost entirely took me over. I slightly identified with Harpo. His humour has always been the second most important thing in my life, I suppose, after music. I imagine the adults found it slightly alarming, though I think I was a slightly peculiar little boy anyway. After The Cocoanuts, I started going to every film I could. And when I'd meet people, instead of shaking their hand I'd give them my leg, which is what Harpo does. It was very irritating for everybody, I think.

I got completely obsessed. I'd refuse to talk for long periods, because I just wanted to mime everything. I don't think my parents ever knew it, but when I first left school - which I did when I was 14, after O-levels - whenever they went out, and I was meant to be practising all morning, I'd probably do a tiny bit of practising and then go off to the local library in Roehampton and just read about the Marx brothers; just look through all the indexes of any book that could just possibly mention them. I must have spent hours and hours of my life reading up every little trivial thing that anybody had ever mentioned about the Marx brothers. And, of course, every book about them I would digest avidly.

This wasn't my first major enthusiasm. I had many. I adopted a jockey - he never knew about it - when I was 9 or 10. I used to love to read the racing pages and there was this man called D - Dennis or David - East, and I used to scour the papers for him. I guess I'm still obsessive, but I was really obsessive then. I tortured people with my enthusiasm. And, of course, I was obsessed with the Beatles and Monty Python.

What is it about the Marx brothers then, particularly Harpo? I suppose I'd been at public school and was rebelling against discipline a bit, and Harpo Marx represented total freedom. He gets away with everything, which I never did. And he doesn't have to talk, which was great. My son Gabriel was incredibly late to talk, and he, like Harpo, managed to communicate everything he needed without words. And Harpo plays music - the harp, of course - and loved music. He's the eternal clown: innocent, a free spirit.

This enthusiasm did have a far-reaching effect on my life. When I was 17, I was supposed to be going to Los Angeles to study with the great Russian cellist Piatigorsky, and he died during the summer. I had a great friend staying with me, a cellist, and he'd been to Oberlin College in Ohio and suggested I went there. I was unconvinced until he said: "You'll be able to watch all the Marx Brothers films all the time. It's amazing; they're all on all night long." That was absolutely the remark that swayed me.

I'm very glad I went there. The only disappointment was that my friend was exaggerating. But my life might have been very different if I hadn't gone there; I would probably have gone to a different school, in New York, which would have been a great struggle as musically it wasn't very good. At Oberlin I found a sympathetic teacher and a sympathetic environment; a lot of my great friends come from that period.

In about 1979, I was in Los Angeles, and discovered that a friend of the people I was staying with knew Harpo Marx's adopted son Bill, a composer. I gave them absolutely no peace until they arranged for me to meet him. So I actually got personal contact, and was photographed wearing Harpo's coat with my leg in Bill Marx's hand. Bill was very fond of his father; he talked very warmly about him. Soon after, I got a festival in England, of which I was director, to commission him to write a piece, "Friends", for cello and harp, which I premiered with Sioned Williams. We're not in contact any more; I kind of lost touch. But it was a nice piece, and I got as close to Harpo as I was ever going to get.

I'm still fascinated. I'm not obsessed any more: obsessions always fade unless you're a total nut - either that or they're replaced by others. But I'm a slightly obsessive collector. I've got a massive collection all over the house: all the Marx films and documentaries I could find. I recently found a wonderful catalogue in the States with things like commercials featuring Harpo. The only things that are missing, as far as I know, are The Story of Mankind and a two-part documentary which was shown on the Disney Channel in the States. One of the best videos I have is the interview he did with Ed Murrow on Face to Face, in which, of course, he wouldn't speak. It's hilarious. The other day the NFT were doing a Judy Garland evening and showed a short film, La Fiesta de Santa Barbara, which, I'd read when I was about 15, had Harpo in it. You saw Harpo for about 10 seconds, but to me it was worth it.

Gabriel's seven now. I showed him the mirror scene from Duck Soup when he was three and he liked it. And last week I played him the whole film, just to see how he'd react, and he quite liked it, but it hasn't become an obsession with him yet. His favourite was Harpo, without any prompting from me. At least, I don't think he got any prompting

Interview by Serena Mackesy

Steven Isserlis plays Elgar's Cello Concerto at the Proms tonight.