In his will made on 9 May 1754, Gibbs left £1000, his Plate, and three houses in Marylebone to Lord Erskine in gratitude for favours from his father the late Earl of Mar. Further bequests included £1,400 and two houses in Marylebone and Argyll Ground Westminster to John Sherwine of Soho plus £100 to be given to a charity of Sherwine's daughters choice, to Robert Pringle of Clifton a Cavendish Square house and £400 and to Cosmo Alexander (1724–1772) a Scottish painter "my house I live in withall [sic] its furniture as it stands with pictures bustoes [sic] etc". Further bequests of £100 each went to William Thomas, Dr. William King, St Bartholomew's Hospital and the Foundling Hospital. The Trustees of Radcliffe Camera were given "all my printed books, Books of Architecture books of prints and drawings books of maps and a pair of globes with leather covers to be placed ... in the library... of which I was architect ... next to my Bustoe".Friedman, pp.17–20
