Leil, the son of Greenshield, a great lover of peace and justice, succeeded him. Leil took advantage of the prosperity of his reign to build a town in the northern part of Britain which he called Kaerleil after himself. This was the time when Solomon began to build the Temple of the Lord in Jerusalem and when the Queen of Sheba came to listen to his wisdom. [II.9]

CARLISLE appears only once in the Historia, as an eponymous foundation of Leil, father of Rud Hud Hudibras (the latter is said by Geoffrey to have founded CANTERBURY, WINCHESTER, and SHAFTESBURY). Tatlock notes (p. 20) that Carlisle had been a Roman station and is mentioned by both Bede and Nennius; the city had undergone a renaissance in Geoffrey's day, with the episcopal see being founded in 1133 (p. 21). Much of the current cathedral dates to the fourteenth century, but the building was founded in 1122. The Roman name was Luguvalium; you can read more about Roman Carlisle on the BBC Cumbria site. Carlisle's city website includes a section on Historic Carlisle.