The refund was our flip-key deposit from our trip to Tokyo. The hoarded money was an envelope of leftover Malaysian Ringgit I discovered as I tucked our passports away. And the backpack was the over-featured monstrosity P insisted on getting to replace the broken-down airline freebie he’d been using for kindergarten.

In the past, I’ve suggested he consider a future in engineering, but that now seems superfluous.

I didn’t want to wait until the idea stopped making sense in my head, so a few weeks ago I had a quick flick through the relevant section of Seat 61, logged on to the KMTB website, and booked the first two sleeper births available on a Friday night out of Woodlands.

Then I hit AirBnB, found