Mews was born at Caundle Purse in Dorset, and was educated at the Merchant Taylors' School, London, and at St John's College, Oxford, of which he was scholar and fellow.

[2] When the Civil War broke out in 1642, Mews joined the Royalist army, and, having been made a captain, was taken prisoner at Naseby; but he was soon released and in 1648 sought refuge in Holland.

He became friendly with King Charles I's secretary, Sir Edward Nicholas, and being skilful at disguising himself was very useful to the Royalists during the rule of Oliver Cromwell, undertaking two journeys to Scotland in 1653.

[5] Mews resigned his presidency at Oxford University in 1673, and in 1684 he was elected Bishop of Winchester, a position which this "old, honest cavalier," as Thomas Hearne calls him, filled until his death.

Mews lent his carriage horses to pull the cannon at a critical moment during the Battle of Sedgemoor, where he was wounded whilst accompanying the royal army.