Sir Piers "le Clerc" de Thornton, Lord of Thornton

 Piers (Peter) le Clerc, was granted Thornton-le-Moors, which was confirmed by Sir John de Arderne, in a charter attested by Philip de Orreby, Justice of Chester; Roger de Montalt, and others, after the succession of Sir John de Arderne's to the Lordship of Aldford, by grant of Randle de Blundeville, Earl of Chester. Peter was the secretary to this Earl of Chester. 

It is stated by Collins, on the authority of the Egerton Pedigree, that Peter was the younger son of David le Clerc, lord of the moiety of the Barony of Malpas. The same descent is frequently given among the Cheshire pedigrees, and in the copy of Booth's Pedigrees, a reference, for confirmation of this fact, is expressly made to an original charter then in the possession of the writer and numbered XXXIII in his collections.

Randle, sixth Earl of Chester, by deed without date, granted to this Peter a boat, and the right of fishing on the Dee from Chester to Eaton; and by another deed, missing the date, granted to Peter, an acquittance from attendance on the court of the shires of hundred and pleas of the forests, from puture of serjeants of the peace, and payment of pannage in the earl's forest. [Harl. MSS. 2131, p. 34] Peter the Clerk has a son and heir, Randle; and a daughter named Agnes, who married William de Blore.

~George Ormerod's The History of County Palatine and City of Chester, Vol II, p. 15

• Background Information. 924 Sometimes during the reign of King John, Thornton part of the fee of Aldford. Richard de Aldford comfirmed a grant of Thornton to Peter le Clerc, the Secretary of the Earl of Chester. Collins, on the authority of the Egerton Pedigree, states that Peter le Clerc was a younger son of David le Clerc, lord of the moiety of the Barony of Malpas. Peter le Cleric's son, Randle assumed the name le Roter, and was the godson of Randle, Earl of Chester. Peter le Clerc is sometimes called Peter de Thornton, from the place of his residence.

~Notitia Cestriensis: Or Historical Notices of the Diocese of Chester, p. 146 footnote 2

Peter was the 3rd son of Sir David de Malpas "le Clerk", took the surname of Clerk.