Westenra was born at Walsh Park, county Tipperary, the residence of his maternal grandfather. One of seven children of William Warner Westenra, 2nd Baron Rossmore, he grew up mostly in England and enjoyed a liberal upbringing, his father’s conduct to his children being described as ‘ever marked with more of brotherly confidence than parental control’.
In 1823 Lord Rossmore expressed ‘high hopes’ of returning Westenra for King’s County at the next election, but the plan came to nothing. In 1830 Westenra proved unwilling to challenge the sitting members, each of whom supported reform, but in 1831 he contested the county in order to ‘remove the stigma of a close borough’ from the constituency. Having been persuaded to express explicit support for the reform bill and ‘the Independent interest’, he resigned after the first day’s polling, citing ‘undue influence’ exercised by the county’s aristocracy.
In 1835 Westenra was returned as a Reformer pledged to ‘oppose the oppressive impost of tithes’, his father having assured O’Connell that upon his two sons ‘Ireland may depend to the last spark’.
Westenra acquired some business interests, sitting on the provisional committee of a company formed in 1840 to supply water to London.
Westenra’s first wife, Lady East, a sister of Hylton Jolliffe MP for Petersfield, had died in London in December 1838 and he remarried at Worthing in July 1842.
Despite having become a director of the London and Manchester Railway in 1845, and a year later joined the management committee of the Larne, Belfast and Ballymena Railway, Westenra did not participate in the division on Lord George Bentinck’s Irish railways bill, 16 Feb. 1847.
Westenra was an active magistrate and took a leading part in the investigation of serious crimes, including several agrarian murders.
Westenra was a keen yachtsman and was for many years master of the King’s County and Ormond hunts. A popular and influential member of the Irish Turf Club, he was one of the foremost horse trainers and breeders in Ireland.
