In 1742 he was appointed Commodore-Governor of the British colony of Newfoundland. He was promoted to rear-admiral in 1745 and appointed Commander-in-Chief, Leith, a post he held until 1746. Byng, stationed off Scotland, thwarted the resupply of the Pretender, James Francis Edward Stuart during the 1745 Jacobite Rebellion. The admiral also assisted the Duke of Cumberland in Britain's crackdown after the Battle of Culloden. He was promoted to vice-admiral in 1747 and appointed Commander-in-Chief of the Mediterranean Fleet. He served as a Member of Parliament for Rochester from 1751 until his death.