There were some clues.
I was given some socks for the wedding anniversary back in December. They were marked as hot weather or inner socks.
Second clue - for Christmas, I was given a very effective down jacket, and some other socks, and some other cold weather clothing.
So, Morocco was unlikely (and anyway, we don't really do hot. Well, bellinghwoman doesn't, unless it's somewhere stunning like HK).
And I was informed that we weren't going to Svalbard. I suspect that rather few people go to Svalbard in January: it's before sunrise, and the polar bears have had plenty of time to get really hungry, at least those stirring from hibernation.
So, my primary guess was St Petersburg. I've been collecting the Nordic countries, starting with Iceland in 2004 and finishing with Finland in 2008. That Finnish trip had then continued on to Estonia, another Baltic country, but we'd not been back to the Baltic since, and we need only a handful of countries to complete the Baltic set. St Petersburg is the great Russian city on the Baltic and would have been the obvious next step. However, you need a visa to visit, and I'd seen no indication of that.
So it was with a sense of delighted puzzlement on my part that we departed by car on the Thursday evening. After 200 yards, we turned right at the end of our street, thereby cancelling out a whole bunch of likely destinations. 50 yards later, we turned right again, thus killing another whole set (anything involving a ship from Harwich, or a plane from Stansted).
By the time we turned down the sliproad onto the A1M and thereby avoided Luton, Heathrow Airport was my primary candidate, though Gatwick Airport was still in the frame.
And Heathrow it was, or rather the Holiday Inn on Sipson Road, where we were to spend the night. bellinghwoman had arranged a package of a room for the night followed by the long term car park.
And so to sleep, me still not knowing where we were going.
You looking at the tags may have a better idea.