Having changed the world once with The Beatles, at the beginning of the 1970s John Lennon wanted to do it all over again. But, this time, in line with his personal vision of global concord.
Desperate to consign the Moptops to history, he escaped to America with the love of his life, Yoko Ono, and plunged into his new world of activism and giving peace a chance.
But if New York welcomed him with bright eyes and open arms, Washington didn't want him around. Richard Nixon was seeking re-election and had a long list of enemies drawn up; Lennon rose rapidly up that list. The Yippie leaders Abbie Hoffman and Jerry Rubin hoped Lennon would lead a movement that would gather momentum around the country. But the partnership never really went beyond planning.
The couple did, however, throw themselves into a variety of local causes and Lennon's songs developed a new political directness.
This meant that the authorities remained on their case and, while Lennon enjoyed the relative anonymity that New York afforded him (the natives were too busy, or too cool, to bother him), he did so in the teeth of constant official surveillance and intimidation.
But for all their stakeouts and phone-taps, the FBI's spectacular incompetence was hilarious.
Lennon was, in fact, smoking so much weed they could have picked him up any time and got him a second drugs conviction that would have meant the end of his green-card ambitions.
A favourite story in the book is the one about the poster distributed to local law-enforcement agencies in the hope that somebody would bust Lennon and strengthen the case for deportation. It contained all his personal details, but the picture was David Peel, a New York musician known for The Pope Smokes Dope album.
Mitchell has done the legwork and there is enough new material to make the book worthwhile.
He spoke at length to the members of Elephant's Memory – the "elephants" of the book's title – the politically conscious bar-band with whom Lennon hooked up to make Sometime in New York City and a nice portrait of Lennon emerges: one of the boys, asking what they thought of his songs.
Nixon's landslide re-election dealt a near-fatal blow to the protest movement and though parallels are drawn with contemporary uprisings, like the Arab Spring and Occupy, that might be over-egging it.
But they had a decent stab at making a difference and, as Ron Dellums, the black Congressman who was also on Nixon's list, says of Lennon, he was right in there: "He showed up for the fight."