[1] In 1932 he competed in the single sculls rowing for Great Britain at the 1932 Summer Olympics but in the final suffered an attack of cramp in the shoulder and finished fourth.

In 1936 Southwood partnered Jack Beresford in the double sculls for Great Britain rowing at the 1936 Summer Olympics in Berlin.

With Adolf Hitler watching, Beresford and Southwood came from a length down to pass the Germans with 200 metres to go and won the gold medal.

Beresford thus won his fifth Olympic medal and wrote later that it was "the sweetest race I ever rowed."

Beresford and Southwood paired up again in 1939 in the centenary double sculls at Henley Royal Regatta.