A relative left his considerable estate to Captain Martin on condition that he and his family adopt the additional name and arms of Leake.
The younger Leake was then holding a clerkship in the Navy Office, but the loss necessitated a search for a better position.
Leake was admitted to the Middle Temple and made a younger brother of Trinity House in 1723.
Garter Principal King of Arms, Sir John Anstis arranged for Leake to be made an esquire to one of the knights.
He also published his essay Nummi Britannici Historia in that year covering the history of English coinage.
His Reasons for Granting Commissions to the Provincial Kings of Arms for Visiting their Provinces was printed in 1744.
He also compiled a collection of drawings of knights' stall plates from St George's Chapel, and travelled abroad to invest foreign princes with the Garter.
Leake himself lived in Mile End, where he was active in vestry affairs and helped raise volunteer units during the Jacobite rising of 1745, and at Thorpe-le-Soken in Essex, where his father had acquired an estate in 1720.