The head of MI5 has warned against overstating Russian interference in the Brexit vote. This is a rare moment in the history of intelligence work: a spy chief asking the public to calm down about a hostile foreign power.

Andy Burnham said Moscow tried to meddle in the 2016 referendum. MI5 would like that kept in proportion. Proportion, in this case, seems to mean the country managed to wreck itself without any outside help.

Consider the evidence. Nine years of arguing produced a border question nobody could answer, a fishing dispute that refuses to die, and a trade deal that exists mostly as paperwork. Did Moscow engineer the lorry queues at Dover? Almost certainly not. Nobody needed to.

If Russia did interfere, the decent response is gratitude. A foreign power that tilted the vote toward this outcome would at least have had a plan. Westminster, by contrast, appears to have had a slogan on a bus.

Officials are reportedly drafting a new line for the inquiry. Early drafts blame the drizzle.