Warren qualified for the 2005 BDO World Darts Championship, where he was the only Welshman in the field. He lost 3–0 in the first round to third seed Mervyn King. Warren has come close to qualifying for Lakeside on two occasions, falling two games short of qualifying for the 2008 World Championship in a loss to Mike Veitch who eventually qualified, and then falling at the same hurdle again in the qualifiers for the 2009 World Championship, losing to Robbie Green. Warren fell two games short once more of qualifying for the 2010 World Championship, losing to Irishman Martin McCloskey who eventually qualified.