The highest political office in Cambridgeshire and Peterborough is that of our directly elected mayor.

The mayor is leader of the Cambridgeshire and Peterborough Combined Authority, which has significant powers and finance for transport, affordable housing, adult education and more.

Both the combined authority and the role of directly elected mayor were created in 2017 as part of the area’s devolution deal.

The outcome of the election on May 6 is likely to determine the direction on major projects such as a proposed rapid transit system, and the combined authority’s affordable housing programme.

The post is being contested by three candidates: one each from the Conservatives, Labour and Liberal Democrats.

The mayoral election uses a supplementary voting system, meaning voters will be asked to register a first and second preference.

If any candidate wins more than 50 per cent of the first preference vote then they will be declared the winner. If no candidate secures that majority, then all but the top two will be eliminated and there will be a second round of counting.

Voters whose first preference was for an eliminated candidate, but who put one of the remaining two candidates as their second choice, will then have their second preferences counted.

Those second preferences are used to top up the totals of the remaining candidates, and whoever has the highest total wins.

The incumbent, Conservative James Palmer, won in 2017, but his lead narrowed when the second preferences were counted, from 29,000 votes to 21,600.

He secured 38 per cent of the vote in the first round, and 56.9 per cent in the second.

The Lib Dems secured 23.5 per cent in the first round, coming second.

Their vote share then increased to 43.1 per cent when second preference votes were counted.

So, while the winner’s vote share increased by half in the second round, the party that came second increased theirs by 83 per cent using supplementary votes.

And it’s this narrowing of the gap which makes the result harder to predict than first past the post.

The Lib Dems have a new candidate this time round, Aidan Van de Weyer, the deputy leader of South Cambridgeshire District Council and a former chair of the Greater Cambridgeshire Partnership.

Labour came third in 2017, with 18.6 per cent, and were eliminated before the second round.

They also have a new candidate, Huntingdonshire district councillor Nik Johnson.

When the 2017 result is broken down by district, the county’s existing divide as seen at the council level – with Labour and the Liberal Democrats controlling much of the south of the county, and the Conservatives controlling the rest – that divide holds.

Cambridge was the only district where Mr Palmer did not win in the first round, and the city and South Cambs were the only districts where he received the fewest second preference votes.

With a final tally of 88,826 to 67,205 after second preference votes were counted, it would take a significant swing for the Conservatives to lose the mayoralty.

The absence of UKIP, who secured eight per cent last time, and the Green Party, who secured 6.3 per cent, means there are a large number of votes to be won even without converting voters from other parties.