It is not often a committed advocate of comprehensive education is invited to address one of the country’s leading independent schools. But after a robust exchange at a conference between myself and the head of Westminster school, Patrick Derham, I was asked to speak to his students. Derham is one of a handful of independent school heads who grasps that something needs to change, though not quite in the way I am about to suggest to his students.

My chosen title is: What’s the problem with private education? It feels like a good time to enter the lion’s den and offer a strongly contrary view to the received wisdoms of this deeply Tory age in which the power of wealth and with it, private education, is as resonant and divisive as ever.

It was not always so. In the run-up to the 1944 Education Act, political leaders of all parties seriously debated, but ultimately rejected, the enfolding of the old public schools into the new structure of free secondary education. In the progressive 60s and 70s, schools such as Eton were considered both something of a joke and emblems of an outdated oppression, as symbolised by Lindsay Anderson’s explosive allegorical 1968 film, If. In 1973, Labour’s Roy Hattersley told prep school heads of the party’s “serious intention” to reduce and eventually abolish independent schools. It seemed logical to assume that the Berlin Wall separating private and state education would soon be dismantled.

How wrong could you be? As the Oxford historian David Kynaston, one of the most acute current critics of private education, observes: “Endless reports point to the privately educated stranglehold and the sheer disparity in life chances, but I’ve yet to see an editorial in a serious broadsheet, including the Guardian, or more than the occasional speech by a politician, that squarely confronts the issue.” He adds: “It is a sad shortfall in what is supposed to be a mature democracy.”

We have recently heard the now familiar arguments on this question from the Sutton Trust, social mobility tsar Alan Milburn, academic John Goldthorpe and Ofsted chief Sir Michael Wilshaw, while the Labour MP Dan Jarvis spoke recently of how “the daughter of a cleaner in … Kingstone, Barnsley, [should] have the same life chances as the son of a barrister in Kingston upon Thames.” Rousing stuff, but how likely is this to be achieved as long as a pupil at an expensive independent school has as much spent on their education in one year as the average UK citizen earns in total and a student at a state school outside London is educated on roughly £4,000 a year – about half a term’s fees at Westminster?…