An unexpected death

It is normal to see a few dead bees outside the hives at this time of year.  Any winter bees that haven't made it through the winter are pushed out of the entrance by the undertakers.  However, this afternoon I was surprised to see one corpse outside hive 3 that looked a bit larger than the others.

When I turned it over it was the queen.  She was marked last summer and was present and correct at my last inspection at the end of September.

Obviously something has gone wrong but I won't be able to do an inspection for the next few weeks.  I expect to find either that the queen was superseded and there is a new unmarked queen, or that the new queen was produced too late to get mated and is a drone-layer, or that the colony is queenless.  If I find anything interesting I'll report back here.