Brunanburgh - also Britain's forgotten battle.
Wincobank and other Forts
Wincobank and the other minor forts which stretched along the Saxon defensive line running from the Mersey to the Humber were built over a fairly short period in the tine of King Edward (born 871, reign 899-924AD).
Evidence from Manchester University is clearer about the western forts on the Wirral and in Cheshire and gives a date of 914. JH Cockburn says Wincobank was fortified in 914 without quoting a source. That year was quite important for the security of Edward's kingdom. There was a Viking invasion of both Northumbria and Ireland in that year.
The Northumbrians and their allies the Angles of what is now southern Scotland were defeated in two battles, one in the Newscastle area and Corbridge. The Irish were attacked and defeated in Cork and Waterford. The strengthehing of his defenses was most likely Edward's reaction. His father's navy patrolled the coasts to prevent surprise, but a large army travelling overland would be a major threat. The western border already had a major fortress at Chester and some of his navy in the Dee. There was Manchester and other remainders of Roman fortified sites in Cheshire and what was to become Lancashire. The new forts filled in the gaps.
A similar situation would exist east of the Pennines but I have so far been unable to find a reference to a construction date. The forts were constructed and the threat was more more immediate. We know Edward was campaigning to get back his father Alfred's kingdom from the Danes, even if if meant him just being their overlord. It is fair to say that he succeeded in part and his legacy meant that even some supposed success after his son Athelstan's death in 939, the Danes in Mercia south of this border returned to the Saxon fold under his other son, Edmund. Most of them by then had given up being Vikings and their treatment by Danish kings in York pushed them towards supporting the Saxons.
Many of the sites fortified had been Roman. A general opinion given to me by an archaeologist, is that whilst the Saxons fortified Roman sites, it was not generally a rebuilding of the Roman works. Templeborough may be an exception and there is, of course, evidence that this took place in 910 at Lady Ethelfreda's behest.