Brendan Venter, Director of Rugby, said: "Soane is a big man, a big player and a magnificent signing for the club. We are building a scrum that will not simply hold its own in the Premiership and in Europe, but will dominate the opposition. Soane has been a key player for Saints, and he will become a key player for us. He and his wife Lucy are only making a short trip down the M1, and I'm certain they will quickly feel right at home in the Saracens family."
Tonga'uiha said: "I have enjoyed my time in Northampton, but everyone can see there is a real energy around Saracens at the moment, and I am looking forward to helping them achieve all their goals."
