The Scotland international, 26, who boasts Six Nations experience having played in the 2015 Championship, brings a neat skill-set coupled with an intelligent kicking game to the Exiles’ ranks.
Acting as injury cover for Chris Noakes who is currently recovering from a shoulder injury, Tonks will join up with his new teammates at the club’s Hazelwood training complex this week ahead of the Aviva Premiership trip to Bath Rugby.
Tonks cut his teeth in professional rugby at Leicester Tigers before making the switch down the road to Northampton Saints where he spent two seasons under the stewardship of Jim Mallinder.
A move to the RaboDirect Pro 12 soon materialised for Tonks when Edinburgh came calling for his services in 2012.
Making 79 appearances for the Murrayfield outfit and racking up just under a century of points, Tonks made quite an impression north of the border.
Head of Rugby Operations Glenn Delaney said: “I am delighted that we have secured the services of a player of Greig’s calibre. He brings a lot of experience to the team and we look forward to welcoming him to the Club.”