Bumblebee queen hibernation hole

In August or so, the new bumblebee queens go off to find a hibernation site. They usually dig a tunnel about 10 cm long, ending in a small chamber. They will then hibernate from end of August to March/April. The new queens are the only bumblebees that hibernate - the rest of the colony, the males and the old queen all die off at the end of summer!

By chance whilst out surveying a badger sett, I saw this large Buff-tailed Bumblebee (Bombus terrestris) queen flying about above the grass and when she landed I thought I would take a few photos but realised she had entered a small hole with a bit of earth dug out. So I watched and waited... And sure enough a minute or so later her back-end emerged, digging earth out of the hole! I realised she must be digging a hibernation tunnel.

I've seen bumblebee nests in the past, but I can't recall ever seeing this before!