Alleyne impressed early for Gloucestershire, scoring a century for them at 18 and a double-hundred at 22, being in both cases the youngest to achieve the feat for the county. He replaced
Jack Russell as captain in 1997, and in 2000 led Gloucestershire to two one-day cups and the
National League title, just missing out on promotion in the
County Championship, his achievements winning him a
Wisden Cricketer of the Year spot. In the ensuing few years he became renowned as a leading tactician in the one-day form of county cricket, leading Gloucestershire to 4 one day knockout cups in 6 years. In 2001, however, his performances fell away somewhat, especially with the bat, and Alleyne relinquished the captaincy to
Chris Taylor in 2004. Indeed, he played just four county matches that year and did not make his first appearance in 2005 until 10 June. ==International career==