The knightly family De La Mare is the first family that we have so far been able to trace as having been associated with Thurlby.
The family held estates under the Abbot of Peterborough; two at Maxey and Northborough, the third at Thurlby, thus the land in Thurlby belonging to the Abbey of Peterborough was partly the Abbey’s manor and associated small holdings, and partly the estate of the De La Mares.
The family held the office of Constable of Peterborough Abbey and had to provide, when called upon, three fully armed horsemen who would serve in the feudal army within the realm for forty days in a year they also had to garrison the Castle of Rockingham. No doubt many Thurlby men had to serve under the De La Mares.
Their coat of arms was displayed in Thurlby Church, along with nine others, and described by Gervase Holles, an antiquarian, in the reign of Charles the First. They owned Maxey Castle, of which only the moat remains today.
Later, when the necessity for fortified manor houses no longer existed, Geoffrey De La Mare built Northborough Manor House, which is a familiar landmark in that village, by the side of the road from Market Deeping to Peterborough.
They built also a large chantry chapel on the north side of Northborough Parish Church, In the porch of Glinton Parish Church will be found two battered effigies of De La Mare knights, one being in the costume of a Woodward – the De La Mares having been the hereditary foresters of Kesteven.
Records show that in 1219 the Manor of Northborough was held by Brian De La Mare, and in 1296 by Peter De La Mare.
In 1346 it was held by Peter’s grandson, Geoffrey, who married the daughter of Geoffrey Le Scrope, one of King Edward the Third’s judges. It was this Geoffrey who built Northborough Manor House and who entered into the agreement about the Constableship.
Sir Peter De La Mare attended the Good Parliament as a representative of Herefordshire, He was elected as Speaker. However, the political influence of the Good Parliament was brief. In November 1376, Peter de la Mare was imprisoned in Nottingham Castle by John of Gaunt. Despite pleas for his release, the Bad Parliament of 1377 refused to pardon him. However, he did gain his freedom in June 1377 following the death of Edward III. Following his release de la Mare was pardoned and compensated by Richard II. He was reelected as Speaker during the Parliament of October 1377.
De la Mare served in several Parliaments during the 1380s. The last recorded mention of him was as a feoffee to Richard Burley in 1387.