There were two record-breaking defeats for the Conservatives and one genuinely unexpected hold. Labour in Selby & Ainsty overturned a Conservative majority of 20,137 (35.7%), by far the biggest of any seat they have gained in a by-election since the 1930s. And the swing of 23.7% was their second highest ever after Dudley West under Tony Blair in 1994.Â
In Somerton & Frome the Liberal Democrats completed what felt like a certain victory by regaining a seat which they had held between 1997 and 2015. The swing of 29.4% was almost the same as in the nearby seat of Tiverton & Honiton from a year ago. The 28.8% decline in the Tory share was their second worst in the parliament.Â
In a sense these two results were entirely predictable. The Tories have been behind in the polls now since November 2021 and since September 2022 their deficit has been somewhere between 15 and 20 percentage points. When any government becomes so discredited that it is an object of popular derision that usually becomes the sole dynamic of any parliamentary by-election where they are attempting to hold one of their own seats. Â
While unpopular Labour governments have in the past still been able to rely on inner city and coalfield seats, the same has not applied to Tory governments when they reach that tipping point, many of whose safest seats on paper are exposed to the Liberal Democrats and their predecessors for whom almost any size of swing is achievable. The Tories did not win any of the thirty-five by-elections held between February 1989 and July 1997 and seemed again since last year to have entered a similar kind of electoral death spiral.Â
Yet despite all this the Tories were able to hold on to Boris Johnson’s old constituency of Uxbridge & South Ruislip, a genuinely marginal seat where Labour required a far lower swing of 7.5% to win it. It was for the Tories the first result since Sunak became Prime Minister that has offered them any serious encouragement.Â
The Results
The results of the by-elections are summarised below.Â
 | Lab | LD | Con | Swing | |||
 | Share | Change from 2019 | Share | Change from 2019 | Share | Change from 2019 |  |
Selby and Ainsty | 46.0% | -5.3% | 3.3% | +21.4% | 34.3% | -25.9% | 23.7% Con to Lab |
Somerton and Frome | 2.7% | +30.1% | 56.3% | -10.2% | 27.1% | -28.8% | 29.4% Con to LD |
Uxbridge and South Ruislip | 43.6% | -4.6% | 1.7% | +5.9% | 45.2% | -7.5% | 6.7% Con to Lab |
Labour will obviously be intensely frustrated that what is by any standard a spectacular win in Selby & Ainsty has been tarnished if not overshadowed by the Tories’ success in Uxbridge & South Ruislip. Many others will be scratching their heads at how two constituencies could produce such divergent swings on the same day.Â
The Uxbridge result is being universally attributed to opposition to London Mayor Sadiq Khan’s proposals to extend the Ultra Low Emissions Zone. For some weeks the parties had all been briefing that the issue was dominating the campaign and most people who knocked on doors in the constituency reported back to the same effect. Added to this Uxbridge has a reputation as being electorally idiosyncratic, and twice before in the last 60 years the Tories have won by-elections in the constituency against the odds. But however much the special circumstances of the by-election itself and the constituency are prayed in aid, Labour will and should be concerned that their national poll lead could be so easily trumped by a relatively parochial issue in such a high-profile contest.Â
Selby & Ainsty however has a good case for being Labour’s best by-election result of the last eighty years, and not just because of the size of the swing and the 2019 Tory majority. For a party which in recent years has thrived in metropolitan and cosmopolitan diversity, educated professionals and students, Selby & Ainsty could hardly have presented more of a challenge. It is an almost entirely white, largely rural seat which voted heavily for Brexit, and which has only ever elected a Labour MP under Tony Blair. For Starmer to secure such a convincing win there suggests that Labour is broadening its reach considerably.Â
For the Lib Dems Somerton & Frome could have been hand-picked for a by-election; a seat where they have always been competitive and where they dominate local government. Â There was never any doubt that they would gain it and the swing matched what they had achieved in their three previous gains in this parliament. With two seats in the West Country again and several councils gained in the region in May, the Lib Dems will be hoping to rebuild their old strongholds in the South West region at the next election. Both Tiverton & Honiton and Somerton & Frome constituencies are abolished under the parliamentary boundary review which may limit the benefits their MPs receive from their mini resurgence.Â
In summing up, all party leaders will feel a degree of relief. The Conservative’s unexpected retention of Uxbridge allowed Sunak to claim a near score-draw; Ed Davey will feel that he can dig-in further in the South-West (and Surrey); and Starmer will be delighted with Selby but determined to make sure there are no more own goals of the sort experienced in Uxbridge.Â