Foreword: May 2017—From British exit to Britain’s break-up

Poised with her pen in front of an outsize Union flag and a No 10 portrait of that old rogue Robert Walpole, Theresa May got all the headlines she’d hoped for when she signed her Article 50 letter—headlines about a “momentous day in British history.” In truth, the state that’s been there since the days of the Whig wheeler-dealer behind her is coming unstuck, and we may be approaching the end of days where “British history” is concerned. What’s more, her signature will only encourage that.

The first 250 years of…