Dr Jack Brown, lecturer in London studies, said the current alternative vote system used to elect the capital’s mayor since the post was established in 2000 delivered a “strong mandate” and the proposal to introduce first-past-the-post was “strange”.

Dr Brown said: “Imposing a change to first-past-the-post for the London mayoral election system after two decades seems strange. The mayoralty was designed to elect one individual/executive with an appropriately strong mandate. The current system delivers this.”

In a first-past-the-post electoral system, voters cast their vote for a candidate of their choice, and the candidate who receives the most votes wins. This can mean that a candidate wins with less than 50 per cent of the vote.

In the supplementary vote system, the voter puts a number by each candidate, with a one for their favourite, two for their second favourite and so on. If more than half the voters have the same favourite candidate, that person is elected. If nobody gets half, the candidate with the lowest number of votes is eliminated and the second choice preferences of that candidate’s voters are redistributed. This process continues until one candidate achieves more than 50 per cent.

The current government is proposing to introduce legislation that would scrap the alternative vote for mayoral elections in favour of first-past-the-post, something it hinted at in its 2019 election manifesto.

Dr Brown said: “The government's manifesto did commit 'support' for first-past-the-post in a general sense, but this hardly amounted to a suggestion that they would rip up the mayoral electoral system in London and start again. To be fair, the 2017 manifesto was clearer - but that was a different government.

“On [the government’s] claim the 2011 alternative vote referendum rejected transferable voting systems UK-wide - this related to how we elected MPs, not mayors. But have a look at the areas that wanted alternative vote in 2011 anyway – they are heavily London-dominated. The argument that London mayoral voters want first-past-the-post is very weak.”

Dr Brown, from the Department of Political Economy at King’s, added that Londoners had their own referendum in 1998 which establishing the current mayoral system, which made clear that the alternative vote was to be used.

“To ignore the results of that London-wide referendum but cite the national referendum of 2011 on alternative vote (for MPs) as a mandate for change seems highly unusual,” added Dr Brown.

Dr Brown is co-author of the book London's Mayor at 20 which examines the inception, development and future of the position. Find out more about the book here.