It has been almost 45 years since Tam Dalyell first asked the West Lothian Question. It is a damning indictment of devolutionary unionists that they are still flailing for an answer.

Dalyell, a Scottish Labour MP with the uncommon foresight and courage to oppose his party’s embrace of devolution, first posed it during the parliamentary debates that teed up the first referendums in 1979:

‘For how long will English constituencies and English Honourable members tolerate … at least 119 Honourable Members from Scotland, Wales and Northern Ireland exercising an important, and probably often decisive, effect on English politics while they themselves have...