It would be useful if the hole in chancellor Rachel Reeves’ budget could be filled through savings on working-age welfare, and so, hey presto, a number is happily rustled up. And it would certainly be useful, given your chief of staff is keen on the appointment and you don’t like to be involved in this kind of thing, if Peter Mandelson’s empty assurances to you about the exact nature of his relationship with Jeffrey Epstein weren’t a barrier to making him your ambassador to the US.