Nevertheless, Adam Bellow, in a book to be published in America this summer, records that the US is seeing a return of dynastic families - not least in politics, as shown by the Bushes - and argues that this is no bad thing.

Under the old nepotism, says Bellow, people got their sons and nephews into jobs regardless of merit; under the new nepotism, relatives (now including daughters and nieces) have to meet minimum standards of competence. (This does not seem to apply to the current US President, but we shall let that pass.) The old nepotism was coercive: daughters married according to their parents’ wishes, sons allowed fathers to chart their careers. The new nepotism is voluntary and “springs from the initiative of children, not the interest of parents”. So we can now, Bellow argues, have the best of both worlds: professional elites who can perform to an acceptable level, but also have the old aristocratic virtues of obligation, generosity and public service.

Needless to say, I regard this as almost complete nonsense. But Bellow raises troubling questions. He is, I think, right to suggest that “there is a new boom in generational succession” (both here and in the US) and that, after 40 years of social fluidity, we have entered an era of increasing social stratification. The reasons are complex, and they present great challenges for state schools, which have based their entire post-Second World War mission on aspirations to social mobility and equal opportunity.

Fluidity has itself created the new social boundaries. People are now highly mobile geographically, socially and occupationally. They lose touch with old school friends and make few enduring friendships in their new neighbourhoods. Typical professionals make almost all their friends at work. They also find their marriage partners at work. This has always been true to some degree, but in a different way. Doctors used to marry nurses, bosses their secretaries. But the number of workplaces where men have to look beyond the office or even beyond their own professional level for a marriage partner are diminishing. Doctors, therefore, marry other doctors, bosses other bosses.

Marriage across social or professional boundaries still happens, but mainly among people in their early 20s, who socialise more freely and who retain the friendships of school and college. But they often end in divorce, followed by re-marriage to a professional colleague.

There is another dimension: the separation of management and production, the “out-sourcing” of services, the decline of the works canteen, have made “the workers” all but invisible to many professionals. Cleaners, tea ladies, typists were once established figures in a company, their names and sometimes their families known to their “superiors”. Now they are phantoms, who come and go at the whim of a contractor.

I am not trying to conjure a golden age when bosses lay awake at nights worrying about their workers’ welfare. But the truth is that lawyers incur obligations to lawyers, journalists to journalists, teachers to teachers; they now feel very few obligations to people beyond their professional circles. This is not a good climate for meritocratic social mobility; but nor is it a good one for Bellow’s old aristocratic virtues. The new nepotism will be as vicious as the old.

Peter Wilby is editor of the New Statesman