Finally got around to putting the mouse guard in place at the front of the hive.
It was a very cold day, around 10C or lower, and there were no bees flying at all, and I couldn't see or hear any bees.
The mouse guard is the normal entrance bar, reversed. This meant first unsticking the entrance bar, by giving it quite a clout and prying it free with the hive tool (the bees had glued it in place with propolis).
As soon as I hit the hive, a great blob of bees appeared at the entrance, looking for trouble to guard the hive from attack.
Fortunately, it was so cold that the bees were very lethargic, and though they were flying up to attack it was a bit half-hearted.
Once again, though, the smoker went out!
That's it for the winter now. Fingers crossed, they will survive the winter and will be happy and healthy in March or so.