Hamilton Rowan returned to Ireland in his thirties, in 1784, to live at Rathcoffey near Clane in north County Kildare. He became a celebrity and, despite his wealth and privilege, a strong advocate for Irish independence. In County Down he joined the Killyleagh Volunteers (a militia group later associated with radical reform) under his father's command, also in 1784. Hamilton Rowan first gained public attention by championing the cause of fourteen-year-old Mary Neal in 1788. Neal had been lured into a Dublin brothel and then assaulted by Henry Luttrell (who, as Earl of Carhampton, later commanded Crown forces in the suppression of the 1798 Rebellion). Hamilton Rowan publicly denounced Luttrell and published a pamphlet "A Brief Investigation of the Sufferings of John, Anne, and Mary Neal" in the same year. An imposing figure at more than six feet tall, Hamilton Rowan's notoriety grew when he entered a Dublin dining club threatening several of Mary Neal's detractors, with his massive Newfoundland at his side, and a shillelagh in hand. The incident won him public applause and celebrity as a champion of the poor.