He was a member of the garrison that withstood the Siege of Lucknow, a key part of the Indian Rebellion of 1857.
He married, in April 1815, Hester Connor, daughter of the Rev. Abraham Augustus Stewart, chaplain to the Royal Hibernian School, Dublin, by whom he had seven sons, including James, a major in the army, who fell at Lucknow in 1857; Louis, rector of Garrycloyne, Blarney, County Cork; William, chief registrar of the Irish court of bankruptcy (d 1892); Charles, major of the 66th foot from 1865; and Mark, registrar of judgments in Ireland.
When Barker was knighted for his leadership at the Siege of Lucknow, Mary Anne became "Lady Barker".
During the Siege of Lucknow on the 16 November 1857 at Lucknow, India, Private Irwin showed conspicuous bravery at the assault on the Secundra Bagh when, although severely wounded through the right shoulder, he was one of the first to enter the building under heavy fire.
In the British television series Downton Abbey, the Dowager Countess, Violet Crawley, tells her grand-daughter during World War I, "War deals out strange tasks. Remember your great-aunt Roberta...She loaded the guns at Lucknow." (Season 2, Episode 1)
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