Harrison came to note as a rugby player when he represented the Royal Marine Artillery team based in
Woolwich. An imposing forward player, he was selected for both the Army and Royal Navy teams before representing the
United Services. The United Services was made up of servicemen from the
Royal Navy and played against the biggest clubs from all over Great Britain. It was while Harrison was playing for United Services that he was selected to play at international level, gaining his first cap for England in the
1909 Home Nations Championship. Harrison was the only new cap brought into the England squad, to face
Scotland at Richmond. England lost 8–18, and Harrison was dropped for the rest of the campaign. Although out of favour at international level, Harrison was still in demand. In 1911 he was selected to play for invitational touring team
the Barbarians, joining the side on their Easter tour of Wales. He was re-invited to join the Barbarians in 1914, to play a forces team from Shoreham Camp. Harrison was given the honour of captaining the Barbarians to 16–13 victory, his opposing captain being
Edgar Mobbs. 1914 also saw Harrison back in favour with the England selectors, and in February he was back in the national team to face Ireland as part of the
1914 Five Nations Championship. England had won the opening game of the tournament against Wales, and Harrison retained his place when they narrowly beat Ireland at Twickenham. He then faced Scotland for the second time, this time away from home at Inverleith. Harrison was given conversion duties during the match, an unusual tactic for a forward, and successfully kicked two goals which prove decisive in a narrow 16–15 win for his England team. With three victories over the other Home Nations, England had won the
Triple Crown, leaving recent inductees
France as the only obstacle to stop England taking the Championship and the
Grand Slam. Harrison was again selected, but kicking duties were now given to
John Greenwood. England won convincingly, making Harrison a Grand Slam winning champion. He may have been selected for further England games, but the outbreak of the
First World War ended all international competitions. Harrison continued to play rugby during the war, and again captained the Barbarians in a 1915 encounter with a South African Services XI. Whilst playing in the Navy, Harrison was known by the nickname, "Dreadnought". ==Military service==