John Lennon and Paul McCartney were still in formal education – the first at art college, the second at grammar school – when they began to compose songs together. As the journalist Ian Leslie explains in his absorbing book, each of their early attempts was written down in an exercise book under the heading ‘ANOTHER LENNON–McCARTNEY ORIGINAL’. No doubt they were thinking of the famous American songwriting combinations whose names they had seen on records by their favourite artists: Leiber and Stoller (writers of Elvis Presley’s ‘Jailhouse Rock’, for instance) and Goffin–King (creators of the Shirelles’ ‘Will You Love Me Tomorrow’). 

There was a crucial difference between Lennon and McCartney and these pairings: the lack of a division of labour. Lennon and McCartney both wrote words and music. Each was quite capable of writing a song by himself, although to begin with, and through the years of their success in the Beatles, it was their habit to collaborate, to exchange ideas as they sat together with their guitars, staring into each other’s eyes. Some of their greatest songs – ‘We Can Work It Out’, ‘A Day in the Life’ – were constructed through the splicing together of individually written, disparate-sounding sections. In the great awakening of the 1960s, the resulting contrasts could add layers of mystery to a record. Some songs were written separately. In 1967, Lennon’s ‘Strawberry Fields Forever’ was coupled with McCartney’s ‘Penny Lane’ on a double A-side single. The two songs, linked only by a common inspiration in Liverpool, each expressed an essential characteristic of its composer: Lennon’s introspectiveness, McCartney’s cheeriness. 

Yet even with those songs, they stuck to an agreement formalised when they released their first record in 1962: every song written by one or both of them would be credited to ‘Lennon–McCartney’, and the proceeds would be shared. The hyphenated credit line would become so firmly lodged in