The Danes were a Germanic tribe, the word Viking is misunderstood, Viking wasn't used to describe who you were it was used to describe what you did, for example, he raised an army and went 'Viking', its a bit like using the term Norsemen (men from the North). So, in the 10th Century, we had Scandinavians but that term wasn't used until many years after the so called Viking invasions. Its probably easier to say various Scandinavian and Germanic tribes were in Britain during the 10th C. And yes, they were all very good at the art of war and killing.
My house is built in an area of an old Anglo-Saxon stronghold 'King Alfred', just down the road from me is King Alfred's tower which was built to commemorate his victory over the Danes'. On a clear day you can look down across the old battlefields and imagine thousands of Danes heading for a fight, it must have been a terrifying sight.
Just so we don't stray to far from the original OP, I would hazard a guess and say that definitely no quarter would have been given.

If you want to have a chat about that particular piece of Brit history, please feel free to PM me.