Here I come

I am pretty certain that this is a Tree Bumblebee, going by the colours anyway. Apparently they do prefer wide-open flowers, so that's right too. 

I was surprised to learn that the Tree Bumblebee only arrived in the UK in 2001 and it has spread rapidly since then. It is an effective pollinator and does not seem to harm our native bee population, so it is currently being welcomed. I wonder if anyone knows any different.