[4] On this newly purchased land he founded the town of Portsmouth as one end of a trade route between England and France.
The original settlement of Portsmouth was a planned town on a medieval grid pattern, of which other examples can be found in places like Salisbury.
[5] One of the first acts ordered by de Gisors in Portsmouth was the donation of land to the Augustinian canons of Southwick Priory so that they could build a chapel "to the glorious honour of the martyr Thomas of Canterbury, one time Archbishop, on (my) land which is called Sudewede, the island of Portsea", Thomas Becket having spent much time in Gisors.
This foundation of the Church of St Thomas of Canterbury was to eventually become Portsmouth Cathedral.
[4] However the royal patronage of de Gisors was not to last, as after his support for an unsuccessful rebellion in Normandy in 1194 he paid the price by forfeiting all his lands, including Portsmouth, to Richard I.