James made his senior debut with the Llantwit Fardre club and trained with Cardiff RFC in the summer of 2006. He then made his debut for Cardiff in the pre-season match at Selkirk while still in the Blues Academy. He made his Blues debut against the Border Reivers in January 2007.

Having progressed well, Down showed the potential he had over the next few seasons, but suffered a horrific broken leg when he fell at the tackle area in the second minute during the Racing Metro v Cardiff Blues match in Paris in November 2011. He has since recovered to become an integral part of the Cardiff Blues pack, making over fifty appearances for the region.