Journey back in time to 1832. The Earl Grey is prime minster (not a class of fancy tea). The leader of the opposition Tory Party is the Duke of Wellington, (who had used his prestige as the victor of Waterloo to become Prime Minister, and ram through Catholic Emancipation).

Grey had forced through an electoral reform to get rid of the rotten boroughs, and widen the franchise to around one in five of the adult males in the United Kingdom.

In the general election of that year the good people of what is now the constituency of Shropshire North returned a Tory MP.

And they continued to do so at every election ever since - until around 4am this morning, when the seat passed to the Liberal Democrats - the successor party to Earl Grey's Whigs.

Helen Morgan gives her victory speech after her by-election win

The blame is falling on the current leader of the Tory party, Boris Johnson (no, its a bit early Waterloo gags), with one of his own backbenchers, Roger Gale, declaring the by-election a referendum on the Prime Minister's leadership.

But plenty of prime minsters have lost mid term by-elections and gone on to win the next general election. Is this one different?

Mr Johnson can still command a parliamentary majority in the upper seventies. And yet there is a sense today that the political weather has changed, that Mr Johnson's political ship is no longer carried along by benign tailwinds, but is facing into headwinds and severe storms.

The ship is leaky, the rats are chatty, and the crew is mutinous.

Anonymous Conservative MPs are being quoted this morning as saying the tipping point in the campaign was the publication by ITN of the video of Downing Street press aides apparently joking about a Christmas Party in the building.

"Partygate" as it has inevitably become known, has become deeply damaging for Boris Johnson's leadership. It has animated the same kind of public anger that "Golfgate" did in Ireland last year (though the public expression of that anger is nowhere near as strong as it was in Ireland).

The issue is the same one - a perception of one law for the "elite" and another for the rest of us. But this was about a party (or parties) that happened a year ago: the information was carefully retained, and released at a time it could do maximum damage - at a point when the Prime Minster was already in a mess over sleaze in his own party, unease among some Tory activists at the direction his government is taking economically, and of course the course of the pandemic, and the unexpected rise of the Omicron variant - forcing the Prime Minster to row back on his summertime promise of no more lockdowns.

But the Shropshire North by-election was entirely a problem of the Prime Minister's own making.

Conservative Party candidate Neil Shastri-Hurst

Owen Patterson, the former Northern Ireland Secretary, did not have to resign after he had been found to have broken parliamentary rules by acting as a paid lobbyist for the Co Antrim-based pharmaceutical company Randox (best known now for its Covid tests).

His punishment was a 30 day suspension. If he had taken his beating the suspension would have been over, and he would still be an MP - one with a near 23,000 majority, and a likely two year period for people to forget about the Randox business before the general election. And given the historic background of the seat, he could afford to lose half his majority and still romp home with one of the heftiest majorities in the country.

But Patterson chose to fight the independent regulator. And Boris Johnson chose to back him in that fight, ordering all the Tory MPs to vote to overturn the independent regulator's decision.

The move backfired.

Patterson resigned, and all the Tory MPs were tarnished with the sleaze. That set off the internal party dis-satisfaction. Or rather it galvanized the growing unease about Johnson's lacklustre performance in the top job, and the sense of drift and missed opportunity that was enveloping a government that is now fully two years on from a general election victory.

From then on the Prime Minister appeared to make a series of political errors. Tory MPs said he was tired, needed a rest, was losing his touch. Being a head of government is a really tough job a the best of times, and these are far from the best of times. On top of that Mr Johnson now has another new baby to interrupt his sleep at night. The Christmas break cannot come soon enough for him.

But Covid may not give him any respite. The unprecedented rise in case numbers will translate into sickness and hospitalisations over the next two weeks. But a senior medical advisor, Dr susan Hopkins, told a parliamentary committee yesterday that scientists will not have enough data on the severity of the Omicron variant until around New Year's Day, at the earliest - more likely the first week of January.

Boris Johnson pictured at a media briefing in Downing Street this week

Her colleague, Professor Chris Whitty, told the same committee that even if Omicron is a relatively mild disease, the sheer concentration of cases, caused by its extremely rapid spread, may mean a couple of months worth of hospitalisations being concentrated into a couple of weeks, which would put severe pressure on the health service.

Not just because there would be more patients requiring hospital treatment, but also because lots of health workers will be themselves off sick, or self-isolating, or caring for relatives afflicted by the same concentrated wave.

As Professor Whitty put it, more demand would meet less supply in the health system. Such a supply-demand curve implies a higher price. Who pays the price? In human terms, the victims of Covid of course. But politically, it may be Boris Johnson who pays the price.

The Welsh government (which is controlled by Labour) has moved today to tighten its own Covid-19 rules, shutting nightclubs from 27 December and enforcing more social distancing measures in shops and offices.

Scotland is looking for money to pay people laid off by the Omicron wave restrictions. Both moves are toxic for the group of 100 Tory MPs who voted against Mr Johnson's government when it brought in some Covid restrictions earlier this week - restrictions that merely moved England into line with the rest of the United Kingdom.

Many of the same group - who are 26% of the Conservative MPs - think Mr Johnson is not really a Conservative, that he is spending too much money, running a high tax regime.

John Redwood MP was out early this morning, arguing that the government should scrap measures like a planned hike in national insurance to combat rising living costs. With inflation now above 5% in the UK, the Bank of England became the first big central bank to raise interest rates yesterday - probably not the best timing for the by-election: in a large, spread out rural constituency, fuel price rises have been a particularly acute issue.

The doyen of British polling experts, Professor John Curtice, tells us that the scale of the Tory defeat in Shropshire North has not been seen since the 1990s, when John Major suffered a string of heavy defeats. Eventually he was challenged for the leadership by John Redwood, backed by the Eurosceptics, who were beginning their ascent to dominance of the party (back then they were dubbed "the Bastards" by Mr Major).

Mr Major won the tussle, but went on the lose the general election two years later.

He was of course confronted by the powerful force of New Labour, led by Tony Blair. The current opposition is a pale shadow of that machine - but it too has turned a corner in terms of public perceptions of trust and competence. As time goes on, it will grow in strength.

The question for Tory backbenchers to ponder over the Christmas period is whether Mr Johnson can recover his political mojo and lead them to victory in the next election. The most successful political party of the last 200 years anywhere is ruthless in the defence of its own interests. If the backbenchers decide Boris is a liability, they will ditch him in an instant.

The traditional route for a leadership challenge is for backbenchers to hand letters demanding a challenge to the chair of the 1922 committee (Roger Gale put his letter in last year over Dominic Cummings' Barnard Castle "eye test").

Currently that job is held by Graham Brady, a prominent figure in the Brexit heaves against Theresa May. He was one of the 100 rebels who voted against the government's Covid measures on Tuesday. He has since let it be known that contrary to popular supposition, the Tory party of the 21st century is not hidebound by convention - disgruntled members do not have to hand him a letter personally calling for a leadership contest- they can send him an e-mail.

So the Parliament's Christmas break may not be much of a break after all for the current inhabitant of Number 10 Downing Street.