Chesham and Amersham: By-election defeat will fuel Tory 'brand Boris' fears

The study of by-elections is a niche activity.

But every now and again one vote comes along that creates a lot of noise.

The Liberal Democrats' victory in Chesham and Amersham is one of them.

It's a huge win for the smaller party who have been struggling for relevance since the 2019 general election, and arguably since well before that.

Winning candidate Sarah Green made the most of voters' disquiet over proposed changes to the planning system.

And, while supporting the project nationally, her campaign concentrated on local anxiety about the progress of HS2.

The result will give some oxygen to the Lib Dems, perhaps an opportunity for a restart too.

And it's a wallop for the Conservatives, and not just because they have lost a seat in a part of the country they'd expect to colour in blue.

On polling day, senior figures in the party expected to shed a load of votes to the Liberal Democrats, but they were not worried that they might actually lose.

Something was going on that the Tories' election winning machine didn't fully notice, which may feel like a nasty surprise.

And it underlines some fears among Tory MPs in traditional Conservative areas that "brand Boris", with its focus on trying to grab new territory, alienates their core support.

While Mr Johnson was overwhelmingly chosen by party members as their leader, that's not the same as him uniting everyone behind him.

He has plenty of detractors inside his own ranks, furious at how provocatively his government has behaved, and frustrated too with some aspects of his political style.

Overall, the local elections in May were a good set of results in England for a sitting government.

But the Tories slipped back in well-heeled parts of the country so, with apologies for introducing another terrible piece of political jargon, were these cracks in the 'Blue Wall'?

This by-election result provides more evidence of support sliding around.

The Lib Dems were able to benefit from demographic changes, generational changes, and for some voters, a residual concern over Brexit.

With a huge Parliamentary majority still, the Tories aren't going to lose their standing overnight.

But the profile of voters in different parts of the country is always on the move.

One member of the government worries about how the party can sustain different identities in different places. They say in the south, "we're like a mid-late term government, in the north we are brand new".

Brexit and Boris Johnson reinvented the Conservative Party and made them electable in parts of the country that wouldn't have dreamt of turning blue decades ago.

So in reverse, don't be surprised if over time, some parts of the country the Conservatives used to rely on shift away from them too.