Social or Cuckoo?

Bees are so confusing if only I knew an expert, late yesterday evening in the garden was this individual  very frustrating - on the face of it its definitely a male social Buff-tailed Bumblebee because: black facial hair, single yellow stripe on thorax and abdomen, tail dirty white to buff, shiny flat and broad tibia, very hairy making it look furry!  However I could also say its definitely a Vestal Cuckoo-Bee because: very lethargic, stripe on thorax darker than stripe on abdomen, no pollen sacs and dark wings.

And one last perplexing feature - antennal segments - 13 in a male, 12 in a female, I can only make out 10 in this image!