Keir Starmer's shock resignation as MP has thrown open the betting on who succeeds him in Holborn and St Pancras, with Labour red-hot favourites but the Greens lurking as a real threat.
Keir Starmer's decision to walk away from Westminster altogether has handed the bookies their next big domestic political market. The former Prime Minister, who led Labour to a landslide in 2024 before being forced out of Downing Street this summer, confirmed he is standing down as MP for Holborn and St Pancras to focus on international affairs and his long-running work on violence against women and girls. It brings the curtain down on an 11-year stint representing the constituency, and triggers what promises to be one of the most closely watched by-elections of the parliamentary term.
Holborn and St Pancras has never returned anything but a Labour MP since the seat was created in 1983, and Starmer himself banked a majority north of 11,000 at the last general election. But with Labour's poll numbers under pressure and the Greens on the rise locally, bookies are not ruling out a shock result.
Reform UK and the Conservatives both find themselves out in the betting cold, while a contest looks likely to develop between Labour and the Greens. Here's how the odds currently stack up.
Holborn and St Pancras By-Election 2026 Odds
Labour go into the contest as overwhelming favourites at 2/7, reflecting both the seat's unbroken red history and the sheer scale of Starmer's cushion at the last election. Even with a by-election swing factored in, bookmakers still expect the seat to stay in Labour hands relatively comfortably.
The Greens sit as clear second favourites at 10/3, priced as the only realistic challengers on these numbers. Reform UK drift out to 50/1 and the Conservatives further still to 100/1.
Who is favourite to win the Holborn and St Pancras By-Election 2026?
Labour are the standout favourites at 2/7. The seat has been a Labour stronghold for over four decades, and the party's local vote share at this year's council elections in the wards covering the constituency still came in comfortably ahead of the field.
The bigger story is where the biggest threat is coming from. The Greens finished as the closest challengers to Labour by vote share in this year's local elections across the relevant wards, and that result is doing the heavy lifting behind their 10/3 price. Green leader Zack Polanski, currently a London Assembly member, has been open about his ambitions to sit as a London MP, and speculation is mounting that he could be the one to stand.
Reform UK's distant third-place finish locally explains their 50/1 tag, while the Conservatives' poor showing in the seat leaves them as outsiders at 100/1. Unless there's a significant shift in sentiment before polling day, this looks set to be a Labour-Green battle rather than a four-way scrap.
When is the Holborn and St Pancras By-Election 2026?
No firm date has been set yet. Before a by-election can be called, Starmer must formally trigger his resignation via a crown appointment, the mechanism that disqualifies a sitting MP from the Commons. Once that's confirmed, Labour's Chief Whip moves the writ in the Commons, MPs vote to approve it, and the by-election must then be held within 21 to 27 working days of the writ being issued.
Labour have already opened the process of picking their candidate, with applications closing on 4 September and a selection meeting pencilled in for 9 September. Expect a firmer sense of timing, and likely some odds movement, once a candidate is confirmed and the writ is officially moved.
