town is built on a low ridge - the remains of a geological fold which has brought older "Forest Marble" clay, capped with Cornbrash rock to the surface, standing out in the midst of the Oxford clay of the surrounding landscape.
More precisely, Trowbridge formed at the point at which the River Biss cuts through this ridge, on its way to its confluence with the Avon, a few miles North of here.
The name means "Tree Bridge", and it is presumed that the Biss was originally spanned by a wooden bridge of some kind. The manor does appear in the Domesday Book, but under another name - Straburg. It may be that one name is a corruption of the other; it may also be that the place had different names at different times.
Unusually, this manor was not already in Norman hands at the time of Domesday (1086). It was in the hands of an Anglo-Saxon noble called Brictric. It's not clear why. Maybe Brictric was just a little too strong to be ousted by the Normans, maybe he had collaborated with them and his reward was to be left alone.
He didn't hold on long. Shortly after Domesday, the land was grabbed by Edward of Salisbury, who then handed it on as a dowry to Humphrey of Bohun, on the occasion of his (forced) marriage to Edward's daughter, Maud. The de Bohun's kept Trowbridge for over a hundred years.
Like most Norman nobles, Humphrey built himself a castle. Little is known about its size, shape or materials, but it must have been fairly robust.
Like Bishop Roger in Devizes, Humphrey's son (Humphrey) sided with the Empress Matilda, in her struggle with King Stephen. But while Devizes Castle fell to Stephen's forces, Trowbridge Castle didn't.
In the subsequent years of civil war, Stephen's allies continued to hold Devizes, and Mathilda's ally (Humphrey) held Trowbridge. The two centres of power glowered at each other across the ten miles or so between them - with occasional skirmishes and intrigues to lighten the boredom.
"and as the two sides assailed each other they reduced all the surrounding country everywhere to a lamentable desert" - Gesta StephaniA later de Bohun (Henry) meddled in royal affairs again.
Everything was hunky-dory in 1200, when King John created our Henry Earl of Hereford (and, incidentally, granted him a charter for a market at Trowbridge). But, in the growing struggle between John and the Barons (the one which led to John's humiliating climb-down and Magna Carta), Henry sided with the Barons.
John was miffed. So he cooked up a legal technicality (relating to the rights of Grandma Maud's family - remember her?), and swiped Trowbridge (and the rest of Henry's lands) away from him.
After John's defeat, this legal stitch-up was unravelled, but, somehow, Trowbridge was lost in the shuffle, and ended up in the hands of the Salisburys.
Eventually, through marriage, Trowbridge became part of the lands of the Duchy of Lancaster. When Henry Bolingbroke of Lancaster became King Henry IV, Trowbridge became Crown lands.
I'm not sure whether the people of Trowbridge noticed any of this.