London mayoral election results: What will be the first clues to a Sadiq Khan or Susan Hall victory?

Londoners face a wait until Saturday afternoon or evening – or possibly even Sunday – until they discover the name of their next mayor.

This is because votes will not start to be counted until 9am on Saturday, even though polling stations closed at 10pm on Thursday.

But several key “bellwether” constituencies could give an early indication of whether Sadiq Khan is on course for an historic third term or whether Susan Hall could deliver a shock victory and seize City Hall for the Tories for the first time in more than a decade.

These include West Central, which covers Westminster, Kensington and Chelsea and Hammersmith and Fulham.

In 2021, Mr Khan was 2,000 first-preference votes behind the Tory candidate Shaun Bailey in West Central. If he wins substantially more votes here than Ms Hall then that could signal victory.

Voting figures for each of the 14 London Assembly constituencies will be announced as soon as each count is completed, with the first declaration expected on Saturday afternoon.

The mayoral votes for that constituency will be announced at the same time – effectively giving a “rolling” indication of each candidate’s total votes captured.

The “official” declaration time is 1.30pm but many expect the announcement to come later than that.

However Neil Garratt, the Tory group leader on the London Assembly, is optimistic the votes will be counted quickly.

Labour will also be waiting anxiously to see how Mr Khan performs in Ealing and Hillingdon, in Brent and Harrow and in South West, which covers the boroughs of Richmond, Kingston and Hounslow.

All three constituencies are marginal but Mr Khan came second to Mr Bailey – now Lord Bailey – in all three in 2021, despite Ealing and Hillingdon and Brent and Harrow being won by Labour in the assembly elections.

Nick Bowes, managing director of insight at London Communications Agency, said: “Given the switch to the [first-past-the-post] voting system, the parties need to pile up votes in their heartlands, so early assembly results will give us a good sense as to how Khan and Hall are doing in inner and outer London.

“Perhaps a more important early sign will be turnout – any significant difference between inner and outer London could have a big impact on the mayoral result.

“If Labour’s top target in West Central goes red, it confirms the party’s growing dominance in inner London and leaves some top Tory MPs looking vulnerable.

“But fail to grab it, and the Tories will feel they’ve checked Labour’s advance. Susan Hall needs a strong show in outer London, so results in Brent and Harrow and Ealing and Hillingdon will be eagerly awaited.”

To secure overall victory, Mr Khan has to repeat his achievement in 2021 in massively outpolling his Tory rival in Labour heartlands in east London and south London.

At that election, rumours spread across the city that Mr Bailey was on course for a shock victory, as Tory areas were among the first to declare.

But once all constituencies were counted, Mr Khan was returned to power comfortably, winning with 1,206,034 first and second preference votes, compared with 977,601 for Mr Bailey.

In the North East constituency, which covers Hackney, Islington and Waltham Forest, Mr Khan picked up 111,000 first-preference votes – 11 per cent of his 1,013,721 city-wide total.

Similarly in City and East, which covers the City of London, Barking and Dagenham, Newham and Tower Hamlets, Mr Khan won almost 100,000 votes, though this was 25,000 fewer than the Labour assembly candidate, Unmesh Desai.

Mr Bailey also did well in City and East, outperforming his party by almost 12,000 votes.

Of the 14 assembly constituencies, Mr Khan polled more votes than Mr Bailey in seven and fewer in the other seven.

But crucially he underperformed in comparison to Labour’s assembly candidate in 10 of the 14 constituencies. In essence, Londoners appeared less keen on Mr Khan than on the wider Labour party.

Back in 2021, it was almost midnight at the old City Hall when Mr Khan was declared the winner.

Then there were two rounds of voting and 20 names on the ballot paper, making the counting of votes a lengthy process, even though it was done by machine.

By comparison, the 2024 election uses the traditional first-past-the-post system, which means there is no second round “run off” between the top two candidates. This should speed up the process, as should the shorter ballot paper – there were only 13 mayoral candidates this time.

But turnout will be the key factor. Many expect it to be lower than the 42 per cent in 2021, which was down from 46 per cent in 2016, the highest it has been since the Greater London Authority was formed in 2000.

But about two million votes will still have to be counted at nine venues across the capital, including ExCeL, Alexandra Palace and Olympia.

The other factor is that the count will be done manually for the first time in a mayoral election. If it becomes clear by around 10pm that many votes are still to be counted, the returning officer may send the counting staff home to return the next day – meaning no declaration of the winner until Sunday.

Mr Bowes, a former aide to Mr Khan, said another factor could be the performance of the anti-Ulez mayoral candidate Howard Cox, of the Reform party.

“What will be important is how well Reform do – Susan Hall has run a Reform-y campaign, trying to squeeze their votes. A strong Reform showing in the ‘doughnut boroughs [of outer London] would be bad news for Susan Hall.”

In 2021, Labour won 11 seats on the assembly, the Conservatives nine, the Greens three and the Lib-Dems two.

Labour won nine of the 14 assembly constituency seats and the Tories five. The 11 remaining “Londonwide” seats were allocated on the basis of each party’s support across London.

In Brent and Harrow, the assembly seat was won by Labour – but Mr Bailey outperformed his party by almost 10,000 votes and received almost 4,000 more votes than Mr Khan.

The Ealing and Hillingdon assembly constituency includes Uxbridge and South Ruislip, which Labour failed to win last year in a parliamentary by-election – which Labour leader Sir Keir Starmer blamed on Mr Khan’s Ulez expansion.

If Labour loses the seat, and nearby Brent and Harrow, it will suggest that many voters in outer London remain angry about last year’s Ulez expansion.