As a child, I spoke several languages. The first belonged at home, in the cottage and the garden, although it travelled with me wherever I accompanied my parents and it stayed intuitively engaged until they were very definitely out of sight and earshot. The second was shared with my schoolfriends: on the bus, in the yard, in the corridor and even in the classroom until a master appeared in the doorway. Then it would be replaced by a third language, which combined elements of the first two yet was distinct from them both. And I suspect there was a fourth language, in which I thought and imagined and wrote, until one day I realised that I could do all these things perfectly well in my first language.

Each of these languages, by which I really mean registers, had its own set of conventions, of which the most obvious concerned its tolerance or intolerance of swearing. One morning after assembly, at Reigate St Mary's Preparatory School, our headmaster, the Rev. J.P.H. Hobson MA (Oxon.), announced that he would like to see in his study the three boys who regularly travelled home on the 424 bus. That was us: Peter and Nigel and me. We'd tumble into the empty green double-decker at its makeshift terminus in a lane by Reigate Station (just off the entertainingly named Birkheads Road), charge upstairs and commandeer the back seat next to the stairwell, the only place on the bus where three villainous eight-year-olds could sprawl ...