DAVID Davis’s threats to resign had become something of a running joke at Westminster.

From feeling left out in the cold when fellow Brexiteers Boris Johnson and Michael Gove presented their own Brexit plan to Theresa May to standing by his Conservative comrade Damian Green over those pornography allegations and from demanding Britain takes back full control of its fishing waters to concerns over the Irish backstop plan, it seemed hardly a month went by when the Brexit Secretary was letting it be known, not directly of course, that he would stand down if his concerns were not addressed.

In April, what appeared to be the real nub of Mr Davis’s angst reared its head – Olly Robbins, the Prime Minister’s right-hand man in the Brexit talks.

The claim was that Mr Robbins, who had once worked at the Brexit Department but had joined Downing Street, was effectively controlling the negotiations with Brussels. That he was edging the UK towards a softer Brexit behind Mr Davis’s back. That papers were being drawn up without the Secretary of State seeing them.

It was even suggested that Mrs May was now relying on Mr Robbins in a way that Margaret Thatcher had relied on the economics guru Sir Alan Walters, much to the chagrin of the then Chancellor Nigel Lawson, who resigned over the row.

The anger of Mr Davis became such that he at one point, and perhaps at several, demanded Mr Robbins be sacked. This was publicly denied by the Secretary of State but in such a way that made people feel that the Yorkshire MP would not have lost any sleep if the chief mandarin had been unceremoniously ditched.

It transpired last month that since the beginning of the year Mr Davis had spent just four hours in talks with his opposite EU number Michel Barnier. In contrast, Mr Robbins had been meeting Brussels counterparts on a day to day basis.

Indeed, after Mr Davis finally did resign the European Commission insisted it would be business as usual.

Philippe Lamberts, who sits on the Conference of Presidents, the governing body of the European Parliament, also made clear the resignation would not make any difference.

“Was he ever in charge, that is the question?” he asked.

"The impression we had on the European side was that he was not really driving the negotiation. Theresa May's office was doing that. I don't think it will make any difference."

But Mr Davis went in the end because, after a weekend of mulling things over, he could not bring himself to champion the PM’s softer Brexit strategy; given he was the one who would have to sell it in Brussels and in the Commons chamber, he concluded, despite hours of talks with Downing Street on Sunday, that the situation was hopeless.

He explained how at the Chequers meeting last Friday he told Mrs May that he was the “odd man out”. He believed that, put simply, his colleague’s plan was offering an “illusion” of sovereignty and that, by and large, the UK post Brexit would be bound too tightly by EU rules.

Branding the May plan a “dangerous strategy”, he insisted, under it, Britain was “giving too much away too easily".

Interestingly, the former Cabinet minister insisted his resignation had strengthened the PM’s hand in the negotiations as Brussels would see she could only go so far and no further or there would be no deal at all.

Noting how she now had to have a Brexit Secretary who would deliver on her strategy, he added: "That is not weakening, that is actually enhancing the effectiveness of the strategy."

Given before his unexpected return to the frontbench, Mr Davis had proved something of a thorn in the Government’s side on a number of issues from the backbenches, it is likely that he will now return to challenging the PM every step of the way to Brexit Day and beyond.