Made a freeman of Portsmouth in 1683 and East Looe in 1685, he was returned to Parliament in the latter year for West Looe as a Tory on the interest of his eldest brother, Bishop Trelawny.
Sir Jonathan Trelawny, 3rd Baronet (1650–1721), Bishop of Bristol, Exeter and Winchester
Sir | Sir Walter Scott | 3rd Rock from the Sun | baronet | Baronet | Jonathan Swift | Jonathan Ross | Goodluck Jonathan | Sir Arthur Conan Doyle | Jonathan Demme | South Carolina's 3rd congressional district | Robert Gascoyne-Cecil, 3rd Marquess of Salisbury | Sir Robert Peel | Michigan's 3rd congressional district | Thomas Fairfax, 3rd Lord Fairfax of Cameron | Jonathan Lethem | Jonathan | Jonathan Richman | Jonathan Coulton | 3rd United States Congress | Jonathan Safran Foer | Jonathan King | Fernando Álvarez de Toledo, 3rd Duke of Alba | 3rd arrondissement of Marseille | Sir Arthur Harris, 1st Baronet | Jonathan Rhys Meyers | Sir Raylton Dixon | Sir Harold Hillier Gardens | Sir Fitzroy Maclean, 1st Baronet | Sir Francis Baring, 1st Baronet |
His father, William Harcourt Isham Mackworth (1806—1872), a younger son of Sir Digby Mackworth, the 3rd Baronet, took the additional surname Dolben after he married Frances, the heiress of Sir John English Dolben, the 4th Baronet.
Sir Jonathan Trelawny, 2nd Baronet (c. 1623–1681), his grandson, Member of Parliament for East Looe, Cornwall and Liskeard
In 1688, the issue arose during the trial of the Seven Bishops—William Sancroft, Archbishop of Canterbury; Sir Jonathan Trelawny, 3rd Baronet, Bishop of Winchester; Thomas Ken, Bishop of Bath and Wells; John Lake, Bishop of Chester; William Lloyd, Bishop of Worcester; Francis Turner, Bishop of Ely and Thomas White, Bishop of Peterborough—by a common jury.
Bishop Jonathan Trelawney appointed him, in February 1703, to the chancellorship of Exeter Cathedral, which he exchanged for the precentorship in May 1704.