The Duke of Wellington has quit the field. The shocking news that he has left the Conservative Party ran round the Palace of Westminster during the afternoon.

His famous ancestor said the test of a great general was to know when to retreat, and to dare to do it. In politics, the Iron Duke concluded that in order to avoid a civil war in Ireland, or even in England, it was his disagreeable duty to persuade his fellow peers to accept various measures to which he and they had hitherto been implacably opposed, including Catholic emancipation and the Great Reform Bill.

The ninth Duke, who served as a Conservative MEP and is now one of the 92 hereditary members of the House of Lords, does not appear to apply this doctrine of precautionary retreat to Brexit. He may, of course, think public opinion is no longer flowing in favour of leaving the EU.

But Tories of a traditional frame of mind cannot be happy to have driven the Duke out of the party.

Nor can Tories of a traditional outlook be delighted to find Dominic Grieve intensifying his attacks on the Government, by demanding the release of all correspondence about the prorogation of Parliament sent or received by Dominic Cummings and eight other advisers “in both written and electronic form”.

Dominic versus Dominic may well drag on as long as Jarndyce versus Jarndyce, so that at the end, no one can remember how it all began.

Grieve spoke of “compelling evidence” that “trust is breaking down”, said that to prorogue until 14th October is “unprecedented” in modern times and “startling”, and argued that “the crisis” which is “engulfing us” makes “continued sitting absolutely essential”.

He drew attention to inconsistencies in the reasons the Government has given for prorogation, and pointed out that it was not David Cameron but Tony Blair who introduced the September sitting.

So Boris Johnson’s description of Cameron as “a girly swot” for doing this was misapplied. Grieve suggested the Prime Minister wished, by contrast, to gain a reputation for “manly idleness”.

A joke, or at least a shaft of satire. But for the most part, Grieve was in deadly earnest, and that was the most distressing thing about his attack. He does not believe a word the Prime Minister says.

The Attorney General, Geoffrey Cox, rose and asked Grieve, who used to occupy that office, what legal right the Government has to demand that advisers hand over their private emails and telephone communications?

But such questions, though justified, can do nothing to repair the breakdown of trust.

Simon Hoare (Con, North Dorset) said he had received no correspondence from his constituents, no matter what their views are of Brexit, saying “I think prorogation is the right thing to do”.

He added, in his capacity as the Chairman of the Northern Ireland Select Committee, that “the legislative needs of Northern Ireland are being ridden roughshod over”.

In Hoare’s view, the Government needs to show “humility”, as “we haven’t got the muscularity” needed to ram unpopular measures through.

This lack of a majority was soon illustrated, for the Government lost the Grieve motion by 311 votes to 302.

The Speaker had earlier announced that he will stand down on Thursday 31st October. This produced laughter, but he then allowed the tributes to him to go on for far too long, the gulf between Labour admiration and Tory disdain becoming more and more embarrassingly apparent, after which he himself attacked a Tory frontbencher – it was hard to tell whether the target was James Duddridge or Graham Stuart – with shameless vehemence: “Quite frankly young man you can like it or lump it.”

This was demeaning. Some of us were told when young never to argue with the umpire, but in those days the umpire was a respectable figure.

Bercow has been a far better umpire than his unfortunate predecessor was. But he has never set an example of good behaviour.