The Liberal Democrats have won the Brecon and Radnorshire by-election, and the leader of their party in Wales, Jane Dodds, is now an MP. It means that the Tories’ working majority is now down to just one on paper, though in practice, Charlie Elphicke, who has had the Conservative whip removed after being charged with sexual assault, still votes with the government as do several of the independents.

Scores on the door:

Jane Dodds (Liberal Democrats) 44 per cent – up 14 per cent

Christopher Davies (Conservative) 39 per cent – down 10 per cent

Des Parkinson (Brexit Party) 10.47 – up 9 per cent from Ukip's 2017 showing

Tom Davies (Labour) five per cent – down 12 per cent

Lady Lily the Pink (Monster Raving Loony Party) – 1 per cent

Liz Phillips (Ukip) 0.76 per cent – down 0.64 per cent

What does it tell us? To be blunt, not very much. It shows us that the Liberal Democrats are back as a serious political force and that the old pattern of by-elections, where they are once again seen as a legitimate home by most left-wing voters in Liberal-Conservative battlegrounds, is back. We knew that yesterday.

What we don't know is how Labour's vote will hold up in the traditional Conservative-Labour battlegrounds. It's par for the course for this to happen to Labour in a Conservative-Liberal Democrat by-election, even in good years. Labour lost its deposits in Christchurch in 1993 and Winchester in 1997 as the Liberal Democrats surged to victory — but Labour didn't do too badly in either of the general elections that followed. We simply don't know yet what will happen in the traditional Conservative-Labour battlegrounds.

It shows us that original brand Ukip are essentially a dead force, and it has now achieved that essential rite of passage of a dying party — finishing below the Monster Raving Loony Party, a satirical party that stands in by-elections with intentionally absurd and strange policies. We knew that yesterday.

And it shows us that the price of a Johnson premiership is that the Conservatives have partially reversed their Brexit Party problem but at the expense of aggravating their Liberal Democrat one. We knew that yesterday, too.

What we don't know is whether the price is worth the product: can the Conservatives pick up seats from Labour in England and Wales' small towns to make up for what they will lose to the Liberal Democrats in England and the SNP in Scotland? And that's ultimately the question that will decide who ends up in Downing Street after the next election.