So, when I was 13, I started to explore art in the way some teenagers hunt out sex. I would tell my parents I was going to play on the estate (I still live in the same block of flats), then take the number 8 bus to the National or National Portrait Gallery.
One day I took the 88 bus for my first visit to the Tate. Inside, I turned a corner and came across a small oil painting called "The Sleeping Fool", by Cecil Collins, an artist I'd never heard of.
Today, I can't imagine encountering somebody's work for the first time and it affecting me in the way that that painting did. It had a figurative symbolism, a fairy-tale quality which features in my own art and writing. I stood in front of it for so long that an attendant came up and asked me if I was all right. I wrote down Collins's name and saw from the dash against his date of birth that he was still alive.
The next day I looked him up at the library and read: "he teaches in London". I tracked him down to the Central Art School (now Central St Martins), where he did a drawing class.
You had to be 18 to enrol, but I was determined to join. I was tall and looked older than I was. Because I was asthmatic, I was excused games at Parmeters, my school, and one Friday afternoon I walked into Central, asked "Where's the Cecil Collins class?" - and that was that.
I was there for six weeks before Collins asked me my surname and if I had signed on at the start of term. I said "I'm sure I did," and he replied:
"Oh, marvellous, I've got one more than I thought." I'm sure he realised I wasn't 18, but he could see how desperately I needed the tuition.
I was passionate about art, music and writing. But Parmeters offered virtually no art education. I find it inconceivable now that no one ever encouraged me there. I remember the English teachers saying to my parents:
"He can't be a painter and write stories." But Collins's lessons changed everything. They were the greatest educational experience of my life.
He was in his 70s, 6ft 4in, a wizard of a figure with a very stooped back. We always used a nude model and it was a revelation at 14 to realise that you could look at the naked form in a non-sexual way. He made us do a lot of exercises which I still do today, working with ink and pencil, teaching us how to use tone.
He'd put the model in the middle of the room and say "Do a five-minute drawing using the hand you're not used to drawing with", then it would be four minutes, then 30 seconds, 10 seconds, one second. We might draw with both hands, or with our eyes closed, or after listening to a Wagner march. He taught me that all the arts are connected and gave me the confidence to say to people at school: "Listen, I am going to do everything."
I began a two-year foundation course at St Martins when I was 16. I was in the middle of painting a huge mural there when Cecil came along to see how I was doing. He asked how I thought the mural was progressing and I said I didn't understand what was going on. He sat me down and said: "This is how it works: you create in order to understand, you do not understand in order to create." Suddenly it was like this huge weight had been lifted away. He was saying "Just do it" and that had a huge impact on me.
Cecil was a visionary, a kind of 20th-century William Blake, and it's sad that he had been - and still is - completely ignored by the art establishment. He was absolutely the Obi Wan Kenobi to my Luke Skywalker, the person who told me I could do what I had the capability to do.
I was in New York when he died, in 1989. I can think of only two other moments when I've felt as desolated at the death of someone I'd never known intimately. I felt this tremendous sense that the world was a lesser place without him.
Philip Ridley, 33, writer, artist and film-maker, is the author of award-winning novels and plays for adults and children. In 1991, his third children's book, "Krindlekrax", won the Smarties Prize, and his first feature film asdirector, "The Reflecting Skin", won 11 international awards. His latest play, "Apocalyptica", opens at the Hamp-stead Theatre, north London, tonight.He was talking to Daniel Rosenthal