Amateur career He was educated at Edinburgh Academy, but was commissioned from there into the army. He played for the
Army Rugby Union from 1922. He scored 4 tries in a match against
Royal Navy Rugby Union in 1924. The
Daily News of 3 March 1924 noting: the outstanding feature of their attack was the dashing work of R. K. Millar, whose personal record of four tries on the wing will no doubt commend itself to the consideration of the Scottish selectors, who were not altogether impressed by his International debut against Ireland the previous week. He played for
London Scottish.
Provincial career He played for
Kent, while playing for
London Scottish. He was played for
Scotland Possibles in their trial match of
19 January 1924 against
Scotland Probables. Few Possibles players impressed, the Probables side winning by 33 points to zero. He played for London Counties in their match against the All Blacks on
15 November 1924. Although London were beaten 31 points to 6, it was Millar that scored London's two tries and only points. He played for the Possibles side again in the trial match the following season on
27 December 1924. Again the Probables convincingly won the match by 27 points to 3.
International career He was capped just the once for
Scotland, in 1924. ==Military career==