The institution of the British cabinet has been weakened. So say Lords Armstrong, Butler, Turnbull and Wilson, all former heads of the civil service. The cabinet is a load-bearing part of the UK constitution: it is the most senior body within government and formally a source of authority. But its importance has been reduced as prime ministers have gained power.

This is not a novel claim, nor a new phenomenon. In 2004, the Butler Inquiry into the use of intelligence in the run-up to the Iraq war made trenchant criticisms of Tony Blair, noting how his informal working habits curtailed the cabinet’s ability to discuss issues.