He came through the academy system at
Bristol Bears, going on to make his senior debut in February 2017, coming off the bench in a 50–17 loss against
Leicester Tigers in the 15th round of the
2016–17 Premiership Rugby season. In 2019 he took a prolonged break from rugby due to a knee injury, Bristol Bears head coach
Pat Lam appointed him as Professional Development Manager, sourcing and organising opportunities for the players and staff away from the pitch. After 2 years away from playing Jefferies returned to Bristol's senior side in round 5 of the
2021–22 Premiership Rugby season, he started in a 13–5 loss against
Newcastle Falcons. He was called up to the
England squad on 30 June 2022 as injury cover for
Charlie Ewels on the
Australia tour. He left Bristol Bears at the end of the 2022–23 season to join Japanese side
Tokyo Sungoliath in the
Japan Rugby League One Division 1. Helping the side to a third place finish in his first season, he featured in all of Sungoliath's games in the
2023-24 season. == References ==