[citation needed] Prosser first played rugby for his home town, Glynneath, before moving to first class side Neath.
Prosser trialled for the Wales team as early as the 1931/32 season[1] but did not gain his first cap until the 1934 Home Nations Championship, when he was selected to face England.
The match was played at the Cardiff Arms Park under the captaincy of first time international John Evans, and the inexperienced Welsh team were poor in comparison to England.
Out of 13 new caps on the day, five, including Evans, never played for Wales again, but Prosser returned in the next two games of the tournament, now led by the more reliable Claude Davey.
Although the joint team lost to New Zealand Prosser brought his familiar style of offensive forward play through the All Black back division,[2] and did enough to gain the favour of the Welsh selectors.