He was arguing against all his training....

But was the plea false?
He had urged on Cromwell that the matter was one of policy.Agreed.But which was the politic road?
If the King lost his head, there would beyond doubt be a sullen struggle ahead.
Sooner or later the regicides would fall--of that he had no doubt.

But what of the ultimate fate of England?
They would have struck a blow against privilege which would never be forgotten.

In future all kings would walk warily.

In time the plain man might come to his own.