Large Garden Bumblebee

While photographing pollinators, I grabbed an image of this bee nectaring on Red Clover growing on the patio. I thought it was just a Garden Bumblebee Bombus hortorum, but when I looked at the images on screen I realised that it had an orange moustache, making it a Large Garden Bumblebee Bombus ruderatus. 

This bumblebee is Britain’s biggest, and it has a long face and tongue,
which allows it to feed from long tubed flowers. It was once very common in southern and central England but it has been lost
from over 80% of its known localities over the last 100 years. In the UK it is now mainly found in the Fens, East Midlands and Cambridgeshire. It's
mostly associated with flower-rich meadow land and wetlands. It has survived successfully in the fens and river valleys of eastern England; however it also uses intensively farmed areas with flower-rich ditches, field margins or organic clover leys. 

I've seen more since then so we must have a nest nearby - certainly our garden has year-round pollen and nectar sources, and I should think there are plenty of disused animal burrows for nest sites, given the number of mice and voles that the cats used to catch when they were younger.