How Zac Goldsmith's defeat in Richmond could hobble Theresa May's hard Brexit plans

The Liberal Democrats’ defeat of Zac Goldsmith in the Richmond Park by-election has provided the latest in a year of seismic political shocks.

While the vanquished incumbent had triggered the vote on the issue of the Government’s approval of Heathrow’s expansion, Lib Dem victor Sarah Olney hailed the win as a rejection of “anger and division” in British politics.

She went on to suggest her triumph signalled a rejection of Theresa May’s plans for a hard Brexit, and the evidence indicates the impact of the result will extend well beyond the affluent London constituency.

Heathrow expansion has been a hugely emotive issue in Richmond, the target of years of passionate campaigning.

So when Mr Goldsmith pledged to quit his party if it pushed ahead with a third runway, it would have normally cemented the issue as the one to decide the ensuing by-election.

But these are not normal times. In the space of a few months the fear, anxiety and opposition to Brexit brushed aside airport expansion to be people’s primary concern.

If Brexit can override Heathrow to be the winning issue in Richmond, it has a strong chance of being the winning issue anywhere that voted to remain.

Early in the by-election campaign, Ms Olney shifted her position on Brexit. Having written a post saying she accepted the result and did not want the referendum re-run, she then hardened her stance to blocking Article 50 in the face of “hard Brexit”. It has done her no harm.

There are many MPs in the Commons who oppose Brexit, but have said they will vote to trigger the Lisbon Treaty Article, launching withdrawal talks.

Richmond suggests that if those MPs have constituencies with a strong contingent of remain voters, they can expect their backing if they decide to oppose invoking the Article.

Brexiteers have branded many Remainers “bad losers”, who cannot accept the result of the referendum.

Maybe they are. Either way, it doesn’t really matter. They are half the electorate, and if they are willing to vote on Brexit at any chance they get, it will have an impact.

The Tories had something of a political shield from the full force of the Brexit blow in Richmond, because Goldsmith stood as an independent.

But Theresa May has firmly established the Conservatives as the party of Brexit, making it the main target of any anti-Brexit voting in the future.

Ms May has said there will not be one until 2020, but there was strong suspicion she may push for one sooner with her party riding high in the polls and Labour in its weakened state.

Yet there are a whole swathe of marginal Lib Dem/Tory seats, many won by David Cameron in 2015, that Tim Farron believes he can steal.

After today’s result, Tory officers will be frantically checking the numbers to see where they stand.