Not quite (might have been better if it had), but what happened at 1am-ish this morning happened when it did because the temperature dropped.
Was woken by SWMBO to the news that water was pouring through the ceiling into the kitchen. Our flat is the ground floor of a converted large turn-of-century house and, we soon found out, our upstairs neighbours are away for the weekend (and therefore still don't know about this).
To cut a long - and, at the time, quite fraught - story short, we tracked down a friend of theirs who rushed over with a key, arriving just as I was bringing in the ladder in order to poke a hole in the ceiling (which never got done).
Upstairs, where we were expecting a scene of devastation ... nothing, complete tranquility. Nothing in adjacent rooms either.
Then, as we were about to return downstairs, I noticed, at the bottom of the wall in their kitchen (where some re-finishing work is being done, an unterminated radiator feed, where the rad had been removed in order for work to be carried out on the wall.
A steady, undramatic-here-at-the-point-of-origin, stream of water was quietly pouring forth. It was a TRV (presumably on a frost setting) that had opened in response to the temperature drop.
The dehumidifier is now purring away in our kitchen. I suppose I'm going to have to lift the TileLOC flooring, but I'm trying not to think about that.