There are not meant to be taboos any more. From Tracey Emin’s unmade bed, to Lady Gaga’s meat dress, from Ricky Gervais’s use of the word “mong,” to Grayson Perry’s pink frocks, culture seems always to be breaking with convention. Shock matters more than chic. As deference has disappeared and the old elites have been overturned, freedom is worshipped in the Facebook age. Henry Miller’s assertion that “whenever a taboo is broken, something good happens,” rings loud and true.

Except, it seems, in politics. In Westminster taboos still carry enormous power. The armed forces, home ownership, and the Queen are off limits; the squeezed middle, banker-bashing and wishy-washy environmentalism are de rigueur.

Each party has its own taboos, of course. For New Labour, scarred by the 1992 shadow budget which was blamed for its general election defeat, it was always tax. For David Cameron’s Conservatives, desperate to shed the “nasty