All our lives, Jo and I had been optimists. Almost by instinct, we both believed that the world was getting better and that it would continue to do so.

Jo, in particular, was positivity personified. With a warm smile and a ready laugh, she was a woman who constantly looked for the best in people and situations. Almost every week, I’d get a call from her apologizing for missing her train home because a constituent in trouble had come into her office and she wouldn’t leave until she had helped them find a way forward.

It wasn’t that either of us felt progress was inevitable — far from it — but we did believe that the world had entered an era when reason was on the march and tolerance and diversity were ascendant.

Earlier this year, for the first time, she and I started to doubt that. We lived on a houseboat on the Thames, by Tower Bridge in London. There, over dinners with friends, we talked at length about our fears of growing populism, a coarsening of political debate and the stoking of hatred against minority groups. Since Jo was a member of Parliament, the forces that were exploiting the Brexit referendum to sow fear were uppermost in her mind; for me, the rise in anti-migrant sentiment in Europe was at the center of my work.