Thomas Mullen was born at Walker-on-Tyne, Newcastle on 20 August 1865, the son of Hugh Mullen. He rode his first winner on Frailty in the Brough Hall Handicap Plate at Catterick on 30 April 1886.
He enjoyed his best season as a jockey in 1892 when booting home 47 winners, including four-timers at Scarborough and Hamilton Park. He also won two big races that year, the Northumberland Plate on Newcourt and the Chester Cup on Daredevil.
In 1893 he won the Manchester Cup on Shancrotha, a victory that led to him naming his house in Rous Road, Newmarket, Shancrotha Cottage after the horse. Sadly, he would not live long to enjoy it.
Thomas rode what was to be his last winner on Ebor in the Cadzoo Selling Plate at Hamilton Park on 7 October 1893. He had his final ride in the last race on the last day of that season, finishing unplaced aboard Barnardo in the Final Plate at Manchester on 25 November 1893.
On Boxing Day, jockeys Fred Rickaby and Thomas Mullen were out riding together at Newmarket. Thomas attempted to jump a fence, but his horse blundered through it, throwing him to the ground. Fred went to his aid and discovered Thomas propped up on the knee of a passer-by. He got to his feet but could only walk a few strides. He was taken by cart to the home of Mr Charles Humphrey at Kirtling where he stayed until his death at 7 a.m. on New Year's Day, 1894.
It was discovered that his skull had been fractured. Indeed, in a few moments of sensibility before his death, he complained of pain in his head.
A verdict of 'Accidental Death' was recorded at his inquest.
An extremely popular man, his funeral at Newmarket Cemetery was the largest seen there for many years.
He left £2,567.
Thomas Mullen was buried on Thursday January 4, 1894