Polling stations have opened in Chesham and Amersham for a by-election that has been overshadowed by opposition to HS2, the high speed rail network, which will carve its way through the patch.

The poll was called following the death of Conservative Dame Cheryl Gillan, who died in April at the age of 68 after a long illness.

In the 13 elections for the parliamentary seat, the Conservatives have never had less than a 10,000-strong majority. Even in 1997, when Labour came to power under Tony Blair, Dame Cheryl took the seat with more than half the vote and a majority of almost 14,000.

But on 6 May, the Liberal Democrats gained control of Amersham Town Council from the Tories. And today, Lib Dems are hoping HS2 will derail the Conservatives’ winning streak.

Sarah Green, the Lib Dem candidate, has vowed to be a “thorn in the side” of the hugely controversial high speed rail project if she wins the seat – and is hoping that this pledge will outweigh her own party’s support for HS2 at the last election.

According to the party’s latest internal polling, this approach is working. The poll, seen by City AM, shows a narrow Conservative lead – with the Lib Dems now expecting 41 per cent of the vote compared with the Conservatives’ 45 per cent. Previous internal polling showed the Conservatives’ lead at 11 per cent.

In a sign of how determined the Lib Dems are to win the seat, their leader Sir Ed Davey has visited more than fourteen times. 

But the Conservative candidate Peter Fleet is fighting back with his own HS2 agenda – saying he wants to work to “protect the special character” of the area which includes “minimising disruption from HS2”.

He told the BBC: “I live in the constituency so I have long been opposed to HS2, while not a single Lib Dem MP voted against it in Parliament.”

Labour’s Natasa Pantelic, a councillor and former primary school teacher, has also based her campaign around the project. She told the BBC she wants to ensure the government “really listens to what our community wants” when it comes to future HS2 development.

Meanwhile, Carolyne Culver, the Green Party candidate, told constituents: “Any candidate who tells you it’s too late to stop HS2 isn’t made of strong enough stuff to be your MP”.

Other candidates hoping to make history today are former HS2 employee Alex Wilson for Reform UK, Brendan Donnelly for Rejoin EU, Carla Gregory for the Breakthrough Party and Adrian Oliver for the Freedom Alliance Party.