The 26-year-old had been in negotiations to extend his current deal with Cardiff, but had failed to agree terms during four months of talks.

It is believed that Saracens, chronic under-achievers again this season, have offered a massive �400,000 for Quinnell's services, who has been capped 32 times by Wales.

Saracens have also announced that France prop Christian Califano will join them during the summer, while they are in talks with Pontypridd's Fijian fly-half Nicky Little.

Califano, who has won 66 caps and is currently playing for Auckland in New Zealand, will join fellow French internationals Abdel Benazzi and Thomas Castaignede at Saracens.

Little, meanwhile, could link up with a second Premiership club after leaving Sale to play for French side Dax, before moving to Pontypridd.

Little's possible departure from Sardis Road will increase speculation that world record Test points scorer Neil Jenkins will quit Cardiff at the end of the summer and return to his home-town club.

Pontypridd will only have the inexperienced Ceri Sweeney as front-line cover if Little departs, while Cardiff have rugby league convert Iestyn Harris and the up-and-coming Nicky Robinson vying for the No 10 shirt.

Quinnell's decision to turn his back on the Arms Park has disappointed Cardiff coach Rudy Joubert.

"It's a big blow to my plans," admitted the South African, who was recently pipped to the Springboks job by Rudi Straeuli.

"Craig was a major part of our team this season and a really good player. It's always sad to see someone like Craig decide not to stay on.

"Given the state of the game in Wales, the club made him absolutely the best - and maybe even a little bit better than we could afford - offer to keep him.

"But he opted for what's available across the (Severn) Bridge."

The four-year deal to join the Watford-based club could earn Quinnell - who is the younger brother of Wales skipper Scott - up to �137,500 per season with European appearances.