Baptised on 12 September 1762 in the church of St Dunstan-in-the-West in the City of London, he was the son of Robert Crew and his wife Elizabeth Oare.
[1] This was the government department responsible for the military establishment of the United Kingdom and its overseas possessions, excluding India.
It was the second largest department after HM Treasury and its head, the Master-General of the Ordnance, had a seat in the Cabinet.
[1] In May 1794 during the French Revolutionary Wars, the Master-General, Charles Lennox, 3rd Duke of Richmond, appointed Robert as Secretary.
In 1793 at the church of St Margaret, Westminster, he married Mary Sophia (1775–1848), daughter of John Foreman and his wife Jane Gordon.