Sean Lonsdale moved to Sandy Park during the summer of 2016, having been spotted by head coach Rob Baxter playing for RGC in North Wales. Lonsdale, who played starring role in RGC’s promotion to the Principality Premiership during the 2015/16 campaign, departed Parc Eirias to test his skills across the border despite a fierce attempt from both the North Walians and the Welsh Rugby Union to keep him in Wales. The talented second row forward was part of the Rydal Penrhos Rugby Academy which is run in partnership with RGC.

He started with the Chiefs on dual-registered terms with Championship side Cornish Pirates, but keen to ensure his development did not stall due to a lack of significant game time, the Chiefs coaches moved Lonsdale to Plymouth Albion, where he figured regularly for them in the National Leagues.

Back at the Chiefs ahead of the 2018/19 season, Lonsdale used the opportunity of pre-season to showcase his worth to the club's coaches - and the tactic certainly paid dividends as he made his Gallagher Premiership debut in the comprehensive home win against Leicester Tigers on the opening day. By the end of the campaign, Lonsdale had indeed established himself within the first-team ranks, featuring not only in the top flight, but also the Heineken Champions Cup.

Since then, Lonsdale has continued to produce some impressive performances for the Chiefs, providing a hard-hitting edge to the Exeter pack, whether it be from the second or back row. Lonsdale returned to Wales to join Dragons ahead of the 2022/2023 campaign and will look to make an impact and catch the eye of Welsh selectors.