Patrick Dunleavy, Prof at the LSE:
"On her first weekend in office, May created a Cabinet in which 21 of the 24 members were new to the role they were playing … The end result of all this shaking up the personnel? May got the political balance she needed to convert to a ‘hard Brexit’ strategy of leaving the EU fast and curbing immigration, so as to attract UKIP voters back to the Tory ranks. But meanwhile almost all ministers spent a year learning their new roles, organizing reviews of policy, and getting almost nothing done.
"The May team’s interfering did not stop at ministers though. In a little recognized but very consequential move for how Whitehall operates, a veritable putsch was organized to get rid of all the senior officials that May disliked (essentially anyone ‘speaking truth to power’). Instead, one by one, May’s team bullied the Cabinet Secretary, Jeremy Heywood, into replacing 5 out of 18 Permanent Secretaries across Whitehall, plus the vitally important head of the UK’s COREPER delegation in Brussels, so as to bring in officials more compliant to Downing Street’s complete hegemony. A further 8 Perm Secs were already new to their roles, not having held posts at the 2015 general election. ...
"But the end result has been that two thirds of the Cabinet of ministers struggling with their new roles are also being advised by new-to-the-job Permanent Secretaries. And the senior civil service’s ability to offer frank advice has been cowed by the PM’s detailed insistence on everything going her way."
[Why did she not go for a “national unity”, grand coalition after the Brexit vote?]