For those in the know, Jimmy Webb is one of the great pop songwriters of the 1960s and 70s, up there with Lennon and McCartney, Brian Wilson, Goffin and King, Holland, Dozier and Holland, and Bacharach and David. The hits he wrote for Glen Campbell alone earned him his place in the Songwriter’s Hall of Fame: ‘By the Time I Get to Phoenix’, ‘Galveston’ and of course ‘Wichita Lineman’, the dying fall of which — ‘And I need you more than want you/ And I want you for all time’ — is so perfect that I am fighting back tears even as I type it. The song was written in an afternoon at the request of Campbell who, after the success of ‘Phoenix’ was looking for ‘something about a town’.

I told him I appreciated his interest but I had just about exhausted the Rand McNally phase of my career. ‘Well, could you make it something geographical?’ he almost pleaded. I told him I would spend the rest of the day on it and get back to him. By about four o’clock I had come up with a song.

Webb was barely 21. His jazzy number about a hot air balloon ride, ‘Up, Up and Away’, recorded by vocal group The 5th Dimension, had just won record of the year and song of the year at the Grammys. In the space of a few months, this son of an Oklahoma Baptist minister had gone from hustling for a break in the hyper-competitive environment of 1960s LA to being deluged with awards, sports cars and recreational drugs. Lyrically and literally, Webb was riding high.

Now the songwriter’s songwriter has written a memoir of this magical period and the carnage that followed. The Cake and the Rain takes its title from another record from Webb’s purple patch, ‘MacArthur Park’; you may know it. The song was a huge and notorious hit for the actor Richard Harris (for whom Webb went on to craft two similarly grandiloquent albums) and again ten years later for Donna Summer, whose Georgio Moroder-produced disco version topped the US charts in 1978. Its central metaphor of a cake left out in the rain, melting, recipe irretrievable, like an apocalyptic episode of Bake-Off, is both famous and infamous; ‘Fucking tremendous! I’ll have that!’ shouted Harris the first time he heard it. (‘It was long enough, tall enough, and wide enough [for him],’ notes Webb wryly. ‘Also, in the zeitgeist of the era, it was obscure enough to confound even the most inquiring intelligence.’)

This book deals with Webb’s early life and his initial phenomenal success through to the mid-1970s, by which point his career is looking like, well, like a cake left out in the rain. Seven years after his rapid ascent with ‘Up, Up and Away’, Webb is plummeting back to earth: having launched himself as a long-haired, bearded singer-songwriter, his (wonderful) LPs aren’t selling; he is developing a serious cocaine habit; he is embroiled in several unhappy love affairs; he nearly kills himself and photographer Henry Diltz when the glider he is piloting crashes into a mountain.

Webb’s problem, as he acknowledges ruefully, was that he was too ‘Vegas’ for the emerging Seventies rock scene while also too ‘hip’ for the showbiz pros who had hits with his songs. He was also very young. These, however, are not problems for the reader of The Cake and the Rain. Webb knows his way around an anecdote and the book draws on his fund of stories about, on the one hand, Campbell, Harris, Frank Sinatra et al, and on the other, Joni Mitchell, Janis Joplin, Harry Nilsson and many more. Of particular note is a bizarre and humiliating encounter with the Beatles during the recording of the White Album, Webb’s account of which has clearly been laid down for 50 years like a bottle of vintage Port; ‘henceforth, Paul and I were never what you could call friends,’ he understates masterfully. Similarly his eyewitness account of John Lennon’s appalling behaviour during the latter’s mid-70s ‘lost weekend’ chills the blood.

Webb is an honest and self-deprecating narrator of his own outrageous fortunes and misfortunes; occasional bursts of pretentiousness are both characteristic and endearing. He can also be very funny. And when he feels sorry for himself, as he frequently does in this book, he sits down and writes a magnificent song about it. The Cake and the Rain is not just a series of tall tales well told but a warts-and-all portrait of what happens to prodigiously talented people when fame gets the better of them — and those around them. Things would get much worse for Webb before they got better — roll on volume two.