He received a Scholarship to the British American Drama Academy in
London, England from July to August 2004 where he attended workshops
with Fiona Shaw, Alan Rickman, and Brian Cox.
Gethin studied English Literature at Oxford University's Balliol College and was President of the Oxford University Drama Society, before training at London Academy of Music and Dramatic Art.
Although he plays notorious cult leader Charles Manson in ''Aquarius (2015-2016)'', he is about eight inches taller than Manson is in real life.