John Perceval was First Lord of the Admiralty from 16 September 1763, to 15 September 1766.
George Marsh first mentions the Earl of Egmont in his diary 14 January 1755 when dining with Sir Arthur Scott, Commissioner of the Navy. Sir Arthur asked George if he would help the Earl by sorting out payments to Naval widows living in the Earl's constituency of Bridgewater in Somerset. Sir Arthur took him to meet the Earl at his house where they all discussed the matter and the Earl handed over all the relating paper work. George later made enquiries and was able to sort the matter out very effectively. The payments to the widows were made and the Earl was very grateful.
A few years later, in 1763, the Earl was appointed First Lord of the Admiralty and George Marsh got back in contact. The Earl made George his private secretary and a few months later appointed him as one of the Commissioners of the Navy for Victualling. This was a great step forward in George's career and he worked closely with the Earl for the next 3 years during the Earl's time at the Admiralty. They seem to have had a good working relationship and continued to maintain contact up until the time of the Earl's death in 1770.
The Earl's earlier political career had been in the Irish House of Commons for Dingle where he sat between 1731 and 1749. In April 1748, he had been created Lord of the Bedchamber to the Prince of Wales. He later sat in the House of Commons for several constituencies. He won the seat of Bridgewater in 1754 against George Bubb Dodington .
John was the son of John Perceval, 1st Earl of Egmont and Catherine Parker (daughter of Sir Philip Parker, 2nd Baronet of Arwarton). He lived at Enmore Castle from 1751 to 1757. He was twice married, firstly to Lady Catherine Cecil (d. 1752), and secondly to Catherine Compton. There were eight sons and eight daughters. One of his younger sons from the second marriage was Spencer Perceval, later British Prime Minister. The Earl died 4 December 1770 at Pall Mall, London, aged 59.
Mount Egmont in New Zealand was named after him by James Cook in recognition of his encouragement of Cook's first voyage. Since the 1980s, the mountain has been called Mount Taranaki which was the former Maori name but the native parkland within which the mountain sits is still called the Egmont National Park thus preserving the name.