997 - Trondheim was founded

Cornwall
Vikings destroyed the Dartmoor town of Lydford.
Ireland
Annals of Inisfallen tells us Brian Boru defeated the vikings and Donnubán mac Cathail at battle of Cathair Cuan.

Norway
Trondheim, was founded by the king Olaf Tryggvason. it was the main city and capital of Norway, until Bergen was founded in the year 1070.  Olaf Tryggvason Fanatical Christianity led him into conflict with the pagan priest Raud the strong who refused to be baptized, Olaf had him tied down and rammed a drinking horn down his throat. Then he pushed a snake into the horn and poked it with a hot iron until it crawled down Raud’s throat and into his stomach.
Wales
Viking attacks began in the Svern district and on southwest England, perhaps caused by increased pressure put on the Vikings in Ireland by Brian Boru and King Mael Seachlinn. The Anglo-Saxon Chronicle reports:
"In this year the army went about Devonshire into the mouth of the Severn and there harried as well in Cornwall as in North Wales and in Devonshire; and then landed at Watchet and there wrought great evil in burning and man-slayings. Thence they rounded Land's End and entered the mouth of the Tamar."