Fortescue was returned unopposed as an opposition Whig Member of Parliament for Barnstaple on his family’s interest at the 1727 British general election. He voted against the Administration in almost every division. He was returned for Barnstaple unopposed again at the 1734 British general election. At the 1741 British general election he transferred to Devon where he was returned unopposed.
- "FORTESCUE, Theophilus (c.1707-1746), of Castle Hill, Filleigh, nr. Barnstaple, Devon". History of Parliament Online. Retrieved 1 February 2019.
|Parliament of Great Britain|
Lieutenant-General Thomas Whetham
Sir Hugh Acland
| Member of Parliament for Barnstaple
With: Richard Coffin 1727-1734
Sir John Chichester 1734-1740
John Basset 1740-1741
| Member of Parliament for Devon
With: Sir William Courtenay, Bt
Sir William Courtenay, Bt
Sir Thomas Dyke-Acland, Bt