While working as a companion for Lord Shelburne, Priestley had a great deal of free time to engage in scientific investigations.
But at this point he fell out with Fox, who he believed should give up the Pay Office, and became more closely associated with Shelburne and Pitt, and there was talk that he would be offered an Irish peerage.
In 1785 he moved to London, Lord Shelburne, then a minister of state, having invited him to undertake the education of his sons.
Initially, the Library consisted of the personal collection of Clements, thousands of rare books, newspapers, maps, and manuscripts, including the papers of General Thomas Gage, Sir Henry Clinton, Lord George Germain, William Petty, Lord Shelburne, General Freiherr von Jungkenn, and Nathanial Greene.
In England he became known by bas-reliefs executed for the Duke of Devonshire and for the Marquess of Lansdowne.
It was not mentioned in the House of Lords until 1793, by Lord Lansdowne and Lord Loughbourough.
William Petty, 2nd Earl of Shelburne and 1st Marquess of Lansdowne, British Prime Minister between 1782 and 1783.
James Earl Jones | Prince Edward, Earl of Wessex | Louis Mountbatten, 1st Earl Mountbatten of Burma | Herbert Kitchener, 1st Earl Kitchener | Earl | Frederick Roberts, 1st Earl Roberts | Earl of Derby | Earl Warren | Earl of Pembroke | Robert Harley, 1st Earl of Oxford and Earl Mortimer | Earl of Warwick | Thomas Wentworth, 1st Earl of Strafford | Edward Smith-Stanley, 14th Earl of Derby | Earl of Shrewsbury | William Pitt, 1st Earl of Chatham | Simon de Montfort, 6th Earl of Leicester | Charles Lennox, 2nd Duke of Richmond | Richard Neville, 16th Earl of Warwick | Earl of Leicester | John Scott, 1st Earl of Eldon | Robert Devereux, 2nd Earl of Essex | Robert, 1st Earl of Gloucester | Hugh Grosvenor, 2nd Duke of Westminster | Edward Harley, 2nd Earl of Oxford and Earl Mortimer | Earl of Devon | Douglas Haig, 1st Earl Haig | 2nd United States Congress | My Name Is Earl | Edward Hyde, 1st Earl of Clarendon | Earl Scruggs |
He was also a biographer, and published works on his great-grandfather, the Prime Minister the 2nd Earl of Shelburne and of his earlier ancestor, the economist, scientist and philosopher Sir William Petty, as well as on the 2nd Earl Granville.
John Petty, 1st Earl of Shelburne (1706–1761), politician, father to former Prime Minister of Great Britain, William Petty, 2nd Earl of Shelburne