Not long ago, I stood in a corner of Spencer House – the London palace owned by Lord Spencer – and watched Prince Charles work the room.

It was an impressive spectacle. Titans of industry queued up to shake his hand; one businessman was visibly sweating at the prospect of touching the royal personage.

Prince Charles chatted effortlessly to dozens of partygoers, dropping in a question here, a joke there, as he subtly moved on without offending the person he’d been talking to.

It isn’t rocket science but, still, putting a room full of gawping admirers at their ease is tricky. And it must be pretty boring, too.

Yet still he does it, day after day, year after year. In 2017, he undertook more public duties than any other royal. He did 374 British engagements and 172 abroad, pipping his sister, Anne, to the post, with a total of 546 engagements to her 540.

That figure is unlikely to decrease any time soon. Last year, Prince Philip, now 96, retired from royal duties, after completing 131 engagements in 2017. The Queen, 92 in April, cut back her duties from 332 to 296 last year.