Theresa May’s brief run of fortune is over. The resignation of Damian Green as First Secretary of State - May’s de facto deputy - ends the Prime Minister’s strongest political period since her electoral humbling.

After a gaffe-free Budget and the conclusion of the first phase of the Brexit negotiations, May cut a more confident figure at the final PMQs of the year. But she has now been forced to sack her closest cabinet ally (indeed, on bad days, her only one). A Cabinet Office inquiry’s conclusion (after nearly two months) that Green lied over the extreme porn found on his computer left May with no choice but to do so. (The Brexit Secretary, David Davis, who previously threatened to resign if Green was sacked, has retreated from the edge.)

The Prime Minister explicitly referred to the “deep regret” she felt in her letter to Green (and notably sought a second opinion after Sue Gray - Whitehall’s no.2 - concluded that the Ministerial Code had been breached). After the humiliating loss of the Conservatives’ majority in June, it was to Green, her decades-long friend (the pair first met at Oxford University in the 1970s), that May turned. As First Secretary of State, Green acted as the Prime Minister’s political life support machine (as Peter Mandelson did to Gordon Brown). The Ashford MP was credited by Tory MPs and civil servants with curbing the indecision and delay that often characterised the previous No.10 regime (he chaired nine ministerial subcommittees). As a “one nation” Conservative, May’s deputy also shared her vision of a less economically dogmatic conservatism.

But Green’s unambiguous breaches of the Ministerial Code rendered his position untenable. Though the inquiry reached no definitive conclusion on the allegations of sexual harassment levelled against Green by the Conservative activist and cultural critic Kate Maltby, it stated that her account was “plausible” (“I clearly made her feel uncomfortable and I apologise,” Green conceded in his letter to May; friends have alleged that Maltby mistook a bar tablecloth for Green’s hand).

Three cabinet ministers have now left the government in two months - each for a different reason (sexual harassment, freelance diplomacy in Israel and lying over porn on a work computer). That Green's departure follows a period of greater calm will aid May. But she must now perform yet another enforced reshuffle (Amber Rudd and Jeremy Hunt - both Remainers - are the most obvious replacements for the Europhile Green). May, who flies to Poland tomorrow on a two-day foreign trip, will wisely wait until the new year before carrying out an overdue refresh of her team.

After one of the most calamitous years in post-1945 political history, the enfeebled May is grateful merely to have survived as Prime Minister. But the departure of Green - prized friend and cabinet consigliere - only enhances the stench of decay surrounding her government.