His godparents were King George II, the Earl Cowper (his grandmother's second husband) and his great-aunt the Dowager Viscountess Bateman.

[1] His sister Lady Georgiana Spencer married the Duke of Devonshire and became a famed Whig hostess.

Spencer's tens of thousands of volumes included the most nearly complete collection of Aldine editions ever brought together.

[8] When Napoleon was in the process of the secularization of religious houses in southern Germany, Spencer used the local British agent and Benedictine monk, Alexander Horn, to acquire many of their rare books and manuscripts.

As the library was not open to the public, the information was found useful, but as its author was unable even to read the characters in which the books he described were written, it was marred by errors, as were almost all his productions.

In 1818 Dibdin was commissioned by Earl Spencer to buy books for him on the continent, an expedition described in his sumptuous Bibliographical, Antiquarian and Picturesque Tour in France and Germany (1821).