Some caveats are in order. By-elections are opportunities for protest that can throw up unexpected and exaggerated outcomes. The Caerphilly result, though, reflects a broader hollowing out of the political centre in Britain, similar to that in many European counterparts. The backdrop is an unsated craving for change first manifested by the vote to leave the EU in 2016. Brexit failed to bring the national renewal its supporters had been promised, but proved an act of economic self-harm. The implosions of the Boris Johnson and Liz Truss premierships were compounded by the cost of living crisis and a continuing deterioration in the public realm.