DOUGLAS Ross’s resignation will be an untimely blow to Boris Johnson, who this morning no doubt was hoping that the political heat was beginning to be taken out of the Cummings affair following yesterday’s extraordinary press conference in the Downing St rose garden.

The Moray MP’s resignation statement, posted on Twitter, will reflect many Conservative colleague’s private anguish based on bulging inboxes.

The key section of the 37-year-old’s Twitter post was: "I have constituents who didn't get to say goodbye to loved ones, families who could not mourn together, people who didn't visit sick relatives because they followed the guidance of the Government. I cannot in good faith tell them they were all wrong and one senior adviser to the Government was right."

In the full spectrum of Government, losing a junior Scotland Office minister is usually not that significant but in this context it continues the political pressure and the swirl of headlines around the Prime Minister, his judgement on Mr Cummings and, more importantly, what damage this row is doing to the UK Government’s public health strategy.

READ MORE: Scottish MP Douglas Ross quits government over Cummings scandal 

During his short five-month tenure at the Scotland Office, Mr Ross had impressed at the Commons dispatch box by his clear and assertive manner in the face of the forceful opposition from Labour, the SNP and the Liberal Democrats. To some, he seemed a far better public performer than his boss, Alister Jack.

Fellow Scottish Conservatives were conspicuous by their silence over the weekend but now Mr Ross has spoken out, other Tory colleagues might follow not just in candidly speaking their minds about the Cummings affair but also in resigning their own posts.

The anxiety that might have lifted in Downing St for a few hours has suddenly been revived by Mr Ross’s unexpected action.

Mr Johnson will, of course, have to find a replacement for the minister, whom he famously singled out for a constituency visit during the 2019 election campaign. Andrew Bowie, the Aberdeenshire MP, and John Lamont, the Borders MP, are available as is David Duguid, who represents Banff and Buchan. However, the list is a short one; yet all appeared to have been silent over the weekend on the damaging Cummings row.

READ MORE: Carlaw says he 'respects' Scotland Office minister quitting over Cummings row 

As Mr Ross made his doubtless difficult decision, borne out mainly by his own sense of indignation at the No 10 aide's actions, he may have been forgiven for having one eye on his own survivability if, like others, his email inbox had been full of disbelieving and angry constituents.

His majority is just 513. As ever with MPs, any perceived threat to their survival at the ballot box is a great one for concentrating the mind.