So, Boris Johnson fears that the Conservatives may face extinction if they delay Brexit (Report, 5 June). He may be right, on this at least, but for the wrong reasons. The fact is that the decline of the Conservatives, and of Labour, is a long-term process which began 60 years ago and may only now have reached its culmination. Both main parties have underestimated the consequences of this decline. The result is that the transformation in party voting seen in the Euro elections and since may be permanent.

British politics has long been seen as dominated by two big parties, each with a block of loyal supporters, and a small number of “floating” voters between them. This was an accurate picture of elections in the early 1950s, when over 80% of the electorate voted Labour or Tory. But this two-party domination began to weaken from the late 50s, a trend that has continued ever since. Turnout fell as fewer people were enthused by the main parties. The growth of this pool of unattached electors gave space for Liberal and Liberal/SDP “revivals”, the growth of nationalist parties in Scotland and Wales, and now the rise of the Green party and the Ukip/Farage phenomenon.