When I was a child, taking a river cruise along the Thames, whether downstream to Greenwich or upstream to Hampton Court, seemed an enormous treat.

It still does. The experience is analogous to that practically extinct pleasure, eating a meal on a train; what would be dull as an everyday experience becomes magical in a new context. William and I hurried to Westminster Pier on an English summer’s day-the kind where you are just beginning to think it is hot, when you regret not having taken a pullover.

We chugged off towards Hampton Court, marvelling that, by this mode of transport, Putney Bridge appears so soon after Battersea. Goodness, what a lot of luxury flats line the banks.

About halfway through our ‘cruise’, we got off at Kew. The full journey takes 3½ hours: enough, you might have thought, to make Henry VIII somewhat restive in his barge. Subsequently, a friend explained that the sort of 20-oared wherry he might have used would have probably have gone at a faster rate than our pleasure boat. Imagine the spectacle that this Tudor equivalent of a speedboat would have made for His Majesty’s subjects. Think of the crowds cheering as they packed the bridges-except that the bridges would not have been there.