He joined the blues during the 1928/29 season, and by 1930 he was selected to represent Wales in a Five Nations Championship match against Scotland in an all-Cardiff three-quarter line alongside Davies, Jones and Turnbull.
'Old Stager' reported that Boon's covering tackling against Scotland's Ian Smith had been impressive and that he had shown an '...extraordinary facility for retaining a grasp on whatever part of his anatomy he could lay his hands'.
In 1933 Boon was chosen to face England at Twickenham, a stadium Wales had failed to win at in ten attempts.
Vivian Jenkins converted the try which was registered on the score board, but strangely the referee would later disallow the attempt after the game.
The decision did not change the result, and Wales had finally beaten the 'Twickenham bogey' and Boon was hailed as a Welsh hero.
Those that never played for Wales again after that game included Watcyn Thomas, Arthur Lemon, Harry Bowcott, Lonza Bowdler and Boon himself.
Boon kept his links with rugby and as well as becoming secretary of London Welsh from 1961 to 1969, he also became president of Barry RFC and served on the Sports Council of Wales.