None of us can predict the potential fallout from Brexit, good and bad. What began as a vote of confidence in our institutions has shown them to be dangerously fallible. A country where people usually rub along together is now marked by a cultural and emotional rift.

If Brexit does continue to dominate our politics for years, will it mean a reform of our institutions, or a battening down of the hatches by a beleaguered elite? Will the House of Lords, having alienated its natural defenders, at last be seriously reformed? Shall we try to restrain the dangerously capricious powers of...