How contented David Cameron looked at 2.27 this afternoon. He had by then been taking questions on his European Union negotiation for almost two hours, which is not, one would have thought, a way to make anyone feel contented, especially as it meant missing lunch.

But the session confirmed that as an exercise in party management, Cameron’s referendum ploy has so far been a triumph. Not only did it avert civil war within the Conservative Party before the general election, which would have rendered victory impossible, and almost certainly have led to Cameron’s departure.

Even now, there seems no real appetite for civil war within the party. There is, of course, an irreconcilable body of Eurosceptics, but they are not in a position to make Cameron’s life a misery, in the way John Major’s life was made a misery by his Eurosceptic opponents.

For the referendum device has rendered the Commons less important than it was when the question was whether it would ratify the Maastricht Treaty, and a handful of “bastards” could torment Major by depriving him of his majority.

By giving the people the final say on whether Cameron’s renegotiation is acceptable, MPs have greatly reduced their own power, and hence their capacity to generate drama by threatening the Prime Minister.

So far as I could see from my place at the back of the press gallery, the only backbencher who managed to rile Cameron was Jacob Rees-Mogg. After an eloquent and dismissive account of the results of the renegotiation, Rees-Mogg concluded that “the thin gruel has been further watered down, Mr Speaker”, and went on: “My right honourable friend has a fortnight to save his reputation as a negotiator.”

The Prime Minister grew animated. He snapped his fingers and banged his pen on his folder. This aspersion on his abilities as a negotiator had wounded him. For one may guess he reckons his performance as a negotiator has been of a exceptionally high order. For month after month he has mastered material of mind-boggling dulness and complexity, has flogged round the chancelleries of Europe, has rejected reams of impractical advice from Eurosceptics, and has found a way through where others would have retired baffled.

Perhaps in order to demonstrate his effortless mastery of detail, Cameron suggested Rees-Mogg “look at Section C page nine”, which shows, apparently, that the EU’s pursuit of “ever-closer union” has been brought to a halt, at least as the far as the United Kingdom is concerned: a claim which Rees-Mogg, with an authority derived from deep emotion as well as actual knowledge, had the effrontery to dismiss as groundless.

No one else managed to disturb Cameron’s  equanimity. Bill Cash, John Redwood, Liam Fox, Peter Lilley and Bernard Jenkin were among the erudite and seasoned Eurosceptics who put questions, and it is more than possible that one or other made some point which will cause trouble in the future.

But today, they could not ruffle Cameron. He knew his brief too well, and was able to discount them as known opponents. He has given them the referendum they were demanding, and intends to get a result which will dismay them.

These admirable gentlemen, who have devoted so much time to the defence of our ancient liberties, are not yet dismayed, but they suffer from an uneasy sense that the game may be moving away from them, that they are somehow out of it, and this makes them sound less trenchant.

Dominic Grieve, a former Attorney General, and Oliver Heald, a former Solicitor General, both expressed their admiration for the legally binding nature of the document obtained by Cameron, provided it is accepted by the European Council.

Grieve said that “in view of the remarkable specificity of the document”, it would be “a very powerful tool”. Cameron was naturally pleased by these testimonies to his achievements as a negotiator.

Alan Johnson, the leader of the Labour In campaign, observed that Boris Johnson’s father, Stanley, and brother, Jo Johnson MP, are campaigning to keep Britain in the EU, and wondered if the Prime Minister might prevail on Boris to join “Johnsons for Europe”.

But when Boris rose to speak, it was to urge the Prime Minister to “resist the volume of regulation” coming from Europe, and “assert the sovereignty of the House”.

Boris did not, however, offer himself as an alternative leader, who would assert with greater vigour and seriousness the sovereignty of the House. In June, as far as one can see, the people will for a moment be sovereign as far as the European issue is concerned.

That means the people will have it within their power to explode Cameron’s reputation, by rejecting the the deal he has so painstakingly negotiated.