Until now, it has always been regarded as more of a footnote than a turning point in the conflict which transformed a nation.
Yet as its 380th anniversary draws near, historians are reappraising the significance of the fall of King's Lynn during the English Civil War.
This often-overlooked chapter in Norfolk history saw the town become one of national importance and shaped its future history, if not that of the conflict itself.
Lynn's strategic significance was not lost on either side, after fighting broke out between the Royalists and the parliamentarians in 1642. As well as a thriving port, it boasted a straight road to London.
Royalist Sir Hamon LeStrange, lord of the manor at nearby Hunstanton, declared the town for the King the following August.
But it was captured just three weeks later on September 16, after the Earl of Manchester and Oliver Cromwell laid siege with 18,000 troops.
Parliamentarians could not afford to lose their prize. So they surrounded it with walls and ramparts.
And they held onto it until they finally achieved victory over the Royalists in 1651.
Little remains above ground today, unlike the South Gate which was built in the 15th century and still presides over one of the main approaches to the town.
But research carried out by the archaeological project King's Lynn Under Siege, including digs around the town, has revealed evidence of fortifications which surpass those of all the other English towns in the same period, including London.
“None of them, and 152 were fortified in all, matches the sophistication of those at King’s Lynn,” said David Flintham, project director of King’s Lynn Under Siege who will be presenting the data his research has uncovered at a lecture next month.
“I have had to look as far away as the Netherlands to find schemes that are comparable to those in King’s Lynn, such is their uniqueness.
“Instead of being regarded as something of a footnote to the history of the conflict, King’s Lynn should be fundamental to any study of the fortifications and sieges of the English Civil Wars.
"If this were not enough, the investigations at King’s Lynn are suggesting a method of rampart construction that has been something of a mystery to fortress historians for a long time.”
Researchers uncovered evidence of ramparts more than 11m wide and 5m high, along with moats and other defences.
“They were formidable," said Mr Flintham. "And a revelation to those of us fortunate to have been part of the investigation.
“Following their capture of Lynn in 1643, the Parliamentary party took steps to repair and improve the existing defences, surrounding the town with a completely new line of fortifications including between the South Gate and the Ouse, and as these were free from the constraints of what went before, the latest techniques could be utilised.
“Designed by Richard Clampe, the construction was state-of-the-art, and amongst the most modern and sophisticated built anywhere in Britain during the entire period, transforming Lynn into the strongest fortress in East Anglia. Thus the town is of national, perhaps even international importance.”
Plans are being finalised for further digs during this year and 2024.
Mr Flintham is the co-founder and project director of the King’s Lynn Under Siege community archaeology project, which has been featured on C4’s The Great British Dig.
He has also written three books, and more than 60 other papers, essays and articles on 17th century fortress warfare.
He will be delivering the annual Diana Bullock Memorial Lecture, organised by the King's Lynn Town Guides at Lynn Town Hall on Wednesday, March 22 (7.30pm).
Tickets priced £9 are available from King’s Lynn Tourist Information Centre on 01553 763044 or on the door.
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