[2] Shirley's family had a long connection with County Monaghan in Ireland, and they owned a large estate at Lough Fea, Carrickmacross.

Shirley entered Parliament for Monaghan (a seat previously held by both his father and grandfather) on 17 November 1868,[3][4] and won election through a promise to defend the Protestant constitution.

He continued to represent the constituency until 31 March 1880,[4] but rarely spoke in Parliament, and is thought to have lost his seat when opposition Liberal supporters ran a successful campaign based on tenants' rights.

He attempted to return to politics in 1885, standing against an Irish nationalist candidate for the newly created seat of South Monaghan, but was heavily defeated.

[citation needed] It also resulted in issues with the local railway, with a boycott by farmers of the station at Carrickmacross taking place in 1890.

[3][11] The last show he attended was the twentieth annual Hunter's Improvement Society, held at the Royal Agricultural Hall in Islington less than a week prior to his death.

[3] By the time of the 1891 census, he was the head of the household of Ettington Hall, along with his wife, their son Evelyn, and his widowed mother, Mary.