The principle of ministerial responsibility generally accepted in theory is that if serious mistakes are made, and this is the fault of administration interpreting policy in a way that goes against the intention of the minister, the responsibility rests on the officers rather than the minister. But if the mistakes are the result of carrying out the policy of the minister, it is the minister who should resign. That applies even if some of the consequences were not fully appreciated by the minister. (After all conviction for dangerous driving does not require that the driver intended to drive dangerously.)

In this case it seems clear that it was the latter, most especially in the case of Theresa May. It is impossible to see how she can remain in office without effectively destroying the doctrine of ministerial responsibility. This was a disastrous car crash with her at the wheel.