A patient opening batsman, Billy made his debut for Middlesex as a 16 year-old and progressed to become a member of the England Under-19 side being selected to play in the Under-19 World Cup in Malaysia in 2008. He had enjoyed a fine season with his former county in 2008 when he scored 732 runs at an average of nearly 37, including a top-score of 113 against Somerset - his maiden first-class hundred. However, he found continued first team opportunities hard to come by at Middlesex and was subsequently allowed to join Essex, initially on-loan in August in 2009, before signing a three-year deal. 

He made his Essex first team debut in 2010 and collected his first century for his new County when taking 106 off the Somerset attack at Taunton that summer. Billy made 11 Championship appearances last season accruing 619 runs from 11 matches that included a century against Leicestershire.