How did the Owen Paterson scandal catch out Number 10 and the Tory whips so badly? On Wednesday, the government imposed a three line whip on a vote in the Commons. The effect was to block his suspension from the Commons for 30 days. They aimed then to overhaul the process for investigating MPs.

On Thursday, the government position collapsed. Ministers u-turned after an outcry from MPs, the press and a deluge of emails from voters. Paterson resigned as an MP.

Paterson had been found guilty of lobbying for two companies. He was on their books. Paid advocacy has been against Commons rules since the late 17th century, although the idea that it doesn’t happen should elicit a hollow laugh.

Why did Boris back Paterson? An act of madness, or something more complicated?

The answer is complex, and according to MPs and advisers there were several factors.

– Sixty or so Tory MPs were hopping mad with the independent Commons commissioner, wanting to take a stand and overhaul the complaints procedure. They say it denies any right to appeal. Number 10 risked making enemies of those MPs, all ready to brand a failure to help Paterson as a betrayal. Storing up future trouble.

– Boris Johnson came under intense pressure from friends of Owen Paterson to help.

– There is genuine human sympathy. Rose Paterson, wife of Owen Paterson, committed suicide during the investigation. The investigation is cited as a contributory factor in her death.

So, Boris Johnson and the chief whip Mark Spencer decided they had no option no matter the risks of public opprobrium.

Or was there another option? Perhaps there was, but for it to work the MP would have had to handle it differently. This he would not do, because Paterson was determined to clear his name and insisted he had done nothing wrong. Even some of his allies have a hard time buying that.

There’s a theory doing the rounds on this. “Owen screwed up, it’s his fault,” says an MP. “He should have accepted early on that he should not have broken the rules and appealed for clemency.”

Another agrees and says the government could then have whipped a vote imposing a seven day suspension (on compassionate grounds) instead of 30 days and it would have passed. That would have made a recall petition, for a by-election, impossible. But it would have involved an admission of guilt.

That didn’t happen. And the Conservative party is left to ponder the damage to its reputation. The best it can hope for is that voters will not be surprised at more tales of MPs behaving badly: “Most of the public won’t care about this, they’ve got other things to worry about,” says a veteran senior Tory.

We’ll see about that.