Unknown Hornet?

Taken with a camera phone so image quality is not very good.

It measured around 50-60mm including sting, has yellow eye patches, black and red thorax - and a huge sting.

This hornet? fell out of the sky onto my plate whilst at a bbq in Northumberland, UK.
It gave everyone a huge fright as no-one has ever seen one of these before.
It waited for a for minutes then flew off again.
Judging by the size of it's sting it means business and we we kept well away once it started to move again.

What on earth is it??