I think it might have been one of these.
The Asian giant hornet (Vespa mandarinia), including the subspecies Japanese giant hornet (Vespa mandarinia Japonica), colloquially known as the yak-killer hornet, is the world's largest hornet, native to temperate and tropical Eastern Asia. Its body length is approximately 50 mm (2 in), with a wingspan of about 76 mm (3 in).
It certainly looks like it.
An allergic human stung by the giant hornet may die from an allergic reaction to the venom, but the venom contains a neurotoxin called mandaratoxin which can be lethal even to people who are not allergic if the dose is sufficient. Each year in Japan, the human death toll caused by Asian giant hornet stings exceeds that of all other venomous and non-venomous wild animals combined, including wild bears and venomous snakes.
Nasty. Doubly glad I didn't stick around in the sitting room to get a picture of it, and that I got Winnie out of its way.