[2] He attended the British Empire Economic Conference in Ottawa in 1932 as an adviser on financial matters to the Australian delegation.

Riddle argued against exchange-rate appreciation, opposing the position of the Commonwealth Bank's chairman Sir Robert Gibson.

Supported by the Bank of England and aided by a lack of enthusiasm for Gibson's proposal by some board members, Riddle's advice was accepted.

[3] Riddle gave evidence at the Royal Commission appointed to inquire into Australia's monetary and banking systems, which ran from 1935 to 1937.

[5] Riddle was a keen sportsman and was considered to be an "expert rifle shot" and a "first class golfer and tennis player".