Castle Park Heritage Part 5: The Castle

Northampton Castle continued to be developed and used as a fortress, palace and prison over hundreds of years. It became one of the largest urban castles in England.

The initial structure of the castle is most likely to have been lost beneath the much larger Royal Castle, which survived as a ruin until the late 19th century. It is therefore believed that much of the castle was the work of King Henry I from the early 1100s and that it was only completed sometime after 1130.

After Simon died between 1109 and 1111, on his way back from the Crusades, it is believed that Henry I took over control of the castle.

Following the death of Simon De Senlis, his wife Maud married David, the son of King Malcolm III of Scotland. As the ownership of the castle was in English royal control, it stopped the castle falling into the hands of the Scottish monarchy as David, who was now King of Scotland, was in the line of succession with his connection to the Earldom of Northampton.

It is recorded that in 1130 further land was acquired for the building of the castle, either for barbican defences around the north gate, or the addition of the outer bailey to the south. Excavation in 2013 demonstrated that the outer bailey was built during the first half of the 12th century.

The castle had its own wells and mill to grind corn and natural water sources like the River Nene were utilised to form a moat.

Around 1140, St Peter's Church was constructed on Marefair. It is believed that either Simon De Senlis II (son of Simon De Senlis) or Simon De Senlis III (his grandson) built the Norman Church on an Anglo-Saxon site. Two fragments from a broken-up late Saxon decorated stone cross were re-used in the foundations of the new church.

Last updated 17 October 2025