He featured numerous times for Harlequins in the A-League and Premiership Rugby Sevens Series before making his debut for the senior side against Northampton Saints in September 2017.

[4][5] Lamb suffered two injuries in short succession at the end of the 2016–17 season, he joined National League side Worthing RFC on loan to help get back to match fitness.

[6][7] Lamb started in the 2019–20 Premiership Rugby Cup final which Harlequins lost against Sale Sharks to finish runners up.

[8] The following season saw Quins reach the league play-offs and he featured in their semi-final win over Bristol Bears.

[12][13] On 5 July 2023, Lamb was selected by coach Kieran Crowley to be part of an Italy squad for the 2023 Rugby World Cup warm-up matches.