The result A new kind of electorate is far more willing to ditch the two big parties

Plaid Cymru’s byelection victory in the Welsh town of Caerphilly is unprecedented. Labour had won every election here for more than a century. Yet the result also feels strangely familiar.

- Paula Surridge

Observers of British politics have become accustomed to unprecedented results. By the end of the previous Westminster parliament, record byelection swings against the government had become the norm, and elections at all levels had shown an electorate who were willing and able to identify the best-placed party to defeat a disliked option.

Byelections for constituency seats in the Senedd are rare. Since its establishment in 1999 (as the National Assembly for Wales), there have been only five, including the one held on Thursday.

In all previous cases, a member from the incumbent party was elected. With Labour dominance in Wales, and in terms of Welsh seats in Westminster, it has been rare for there to be much interest in Welsh politics outside Wales.