Harri had previously been part of the Bath Academy and graduated through the Welsh Exiles programme before signing with the Scarlets. Welsh qualified through his father, who hails from Bonymaen, he studied at Llandovery College and played for Scarlets U18 before playing for Wales U18 and going to be capped at U20s level. Gained experience in the English Championship with Nottingham during the 2020-21 season. Made his URC debut against the Ospreys in January 2022 and was called up as an injury replacement for Wales's summer tour of South Africa. Harri's young brother Sam is also part of the Scarlets set-up.