Background
Rendlesham was a younger son of Peter Thellusson, 1st Baron Rendlesham, and Elizabeth Eleanor, daughter of John Cornwall.
Rendlesham was a younger son of Peter Thellusson, 1st Baron Rendlesham, and Elizabeth Eleanor, daughter of John Cornwall.
Rendlesham succeeded his elder twin brother in the barony in 1839. As this was an Irish peerage it did not entitle him to an automatic seat in the House of Lords. Lord Rendlesham married Elizabeth Charlotte, daughter of Sir George Prescotte, 2nd Baronet, and widow of Sir James Duff, in 1838.
Lady Rendlesham died in December 1840.
Lord Rendlesham survived her by twelve years and died in April 1852, aged 54.
14th United Kingdom Parliament. 15th United Kingdom Parliament]
He was instead elected to the House of Commons as Member of Parliament (Member of Parliament) for Suffolk East at a by-election in 1843, a seat he held until his death nine years later.