It’s unusual for a Governor of the Bank of England to announce his next job before Downing Street has named his successor. In Mark Carney’s case, the new role turns out to be an unpaid, part-time one as the UN’s special envoy for climate action and finance, so no protocol has been breached — though the announcement will serve as a reminder to Chancellor Sajid Javid or whoever succeeds him to let the long–suffering Canadian escape his Threadneedle Street prison as swiftly as dignity allows after election day.