Whitehall’s prized impartiality is the official reason for not giving the Tories the detailed figures on public spending that they have requested during the normal discussions with senior civil servants in the run-up to the general election. First Secretary Lord Mandelson insists that what the Tories are told is entirely up to Sir Gus O’Donnell, the cabinet secretary – not ministers. Sir Gus must be scrupulous in not discussing with ministers anything the Tories say.

Yet according to rumour control, Prime Minister Gordon Brown originally told the Tories that decisions on what information they were given would be a matter for ministers. So why are the Tories not making a meal out of this seeming duplicity? Maybe because they do not want to embarrass Sir Gus and his colleagues – who they will have to work with if they win the election.