Son of Nathaniel Clayton (Town Clerk of Newcastle upon Tyne from 1785 to 1822), he was educated at Kirkoswald School in Northumberland and received classical education at Uppingham. He began work in the firm of solicitors that had been established by his father Nathaniel in the Bigg Market in 1778, and which became Clayton and Dunn, and qualified as an attorney in 1815. John become Under-Sheriff in 1816 before succeeding his father as Town Clerk in 1822, remaining in post until 1867. He never married, but shared the family's townhouse in Fenkle Street, Newcastle, with his unmarried brother and legal partner, Matthew.