Could be Terrestris (which is what I saw) but it could also be Pratorum - depends on the colour of its tail - they are very similar. Pratorum is another Bombus that is seen in Spring - its common name is Early Bumble.
It was laid spread out and what appeared to be wrapped in the blossom. It was completely motionless as if asleep. I took half a dozen pics but non show it's tail.Of all the Bumbles in our garden at the moment this was the smallest, most seem to be mainly black in colour but as yet I have yet to see one settle so that I could identify or take a pic.
Not a buff tail then, as they're not small.
It was not particularly small other than in comparison to some of the dark ones which are giants, none have paused long enough for me to have a close up and my eyes are OK but not quite as sharp as in the past, I tend to rely on the camera which has cracking eyesight.
I an no expert so I will go with others opinions. When I read that there are 270 plus types of bumble in the UK......well what can you say......oh there goes a bumble and leave it at that
