For a time those certainties not only offered an insecure young man usefully strong opinions about everything, they also provided me with a substitute family of the ideologically like-minded at a time when I had broken with my real family's beliefs and traditions. 

But my career as a serious leftist at university did not last long. My own self-consciousness about the absurdity of being an Etonian Che Guevara was combined with an uneasy realisation that too many of my comrades were also well-heeled public school or suburban grammar school types for whom Leninist bossing around of the masses came a bit too easily. 

But even as I settled down as a more mainstream member of the Guardian-reading middle-class liberal Left (and joined the Labour party) in my mid-twenties, I think I carried with me a sense of viewing those tribal beliefs somewhat from the outside, and a lasting curiosity too about why political people have come to believe the things they do. For David Hume is surely right: reason is the slave of the emotions. At least for those of us who are free to choose our political commitments, without having them forced upon us by circumstance, it is the emotional impulse that seeks out the facts and arguments, not the other way round.

The reason I am dwelling rather indulgently on my own past is that in the light of the publication of my recent book The British Dream (about the successes and failures of postwar immigration) Standpoint has asked me to write about my apparent "breaking" with the Left. 

I don't think I have broken with the Left, but I like to think that self-consciousness about the roots of my own beliefs has given me an especially sensitive nose for the cant of the righteous, especially those who dwell in privileged bubbles of the highly educated. If you are a walking contradiction perhaps you are more aware of it in others, whatever their background. 

Far from being an attack on the Left, my book is an attempt to reinforce one pole of the centre-left argument about immigration and multiculturalism. To express it in a slogan, I am pro-immigrant but against mass immigration. I believe in human equality and the unity of the human race, but I am sceptical about the economic benefits of large-scale immigration for the bottom half of British society, and worry about too much rapid change leading to segregation of communities and a withering of the kind of fellow-feeling needed to sustain welfare states.