He was in his mid- to late-thirties, tall, thin and totally unthreatening. Mr Spearman - I think his first name was David - taught me English when I was in the upper sixth at Watford Grammar School for Boys.
A kind, softly spoken, almost shy man, he had just arrived at the school as the new head of the English department. The first set text we had to tackle was John Milton's Comus, a long poem, known as a "masque" - a royal court celebration dating at least from the reign of Elizabeth I.
Mr Spearman's first lesson was unforgettable because he said something that amazed us all. "To be absolutely honest," he said, "I don't understand this poem and I want you to help me to understand it."
This was something unheard of at Watford Grammar, a school where teachers usually presented themselves as brusque, all-knowing experts in their fields. Yet here was a brand new teacher, a head of department, no less, who was suggesting that this 17th-century poem was beyond him.
I went home and told my dad, Harold Rosen, who at the time was training English teachers at the Institute of Education, University of London. "That's brilliant," he said. "What a great dodge, what a great teaching trick! He's trying to get you to explore the poem yourselves."
Over the rest of the academic year we went through the poem and whenever we asked Mr Spearman a question, he would say: "Well, to be absolutely honest, lads, I don't really know." Then we would look things up in the notes at the back of the book or go and find the Cambridge History of English Literature, trying to find out everything we could about the poem. I wrote an essay and showed it to my dad. "That's good," he said. "The teacher's method is working."
Some 15 years later I was at a school reunion and Mr Spearman, by now a principal, was there. He came up to me and said: "I'll never forget that year with you boys in Watford. I had no idea what that poem, Milton's Comus, was all about, and you boys were amazing."
He said that the experience had taught him his best lesson in teaching: that sometimes the best way to teach is not to say, or even pretend, that you know everything, but to encourage the students to explore it for themselves.
When I told my dad what Mr Spearman had said, he roared with laughter - pleased that he had been proved both right and wrong.
Mr Spearman's approach has had a huge influence on my own teaching - of children and teachers. In my poetry workshops, I encourage teachers to find ways for students of all ages, from four upwards, to explore a poem, novel or story before the teacher interposes. Research shows again and again that the best responses in the early stages come from children talking to each other rather than being quizzed by teachers.
Mr Spearman's lessons were enjoyable without being too formal. About 12 of us would sit around two tables. Occasionally we were a bit boisterous and he would just say, "OK, chaps ..." and that was enough to get us back in line. He was generous, kind and appreciative. His whole approach was utterly honest and interesting and put us in the driving seat. The Milton poem, not the most interesting in the English language, became a fascinating puzzle.
Although we were on the cusp of the 1960s, with dramatic social and cultural changes in the air, Mr Spearman was a bit old-fashioned. His teaching methods, however, were revolutionary.
Michael Rosen, the Children's Laureate 2007-09, is touring the UK with his stage show, based on his book Centrally Heated Knickers (centrallyheatedknickers.co.uk). His We're Going on a Bear Hunt show is at the Lyric Threatre in Shaftesbury Avenue, London, 3 July-1 September. He was talking to David Harrison
Born: 7 May 1946, Harrow, Middlesex, England
Education: Pinner Wood County Primary, West Lodge County Primary, Pinner, Middlesex; Harrow Weald County Grammar, Watford Grammar School for Boys; Middlesex Hospital Medical School; University of Oxford, University of Reading, University of North London; National Film School
Career: Children's novelist and poet; presenter Word of Mouth, BBC Radio 4.