Former Gloucester scrum-half Dimitri Yachvili clinched a surprise Heineken Cup victory over Northampton with the final kick of the game.

With only eight minutes left on the clock, Saints had looked comfortable holding on to a 20-13 lead.

But a converted try by Yachvili levelled the scores before the 22-year-old sealed the win with his penalty deep into injury time.

Northampton had looked the stronger of the two sides for much of the contest, with Yachvili's opposite number, Matt Dawson, in impressive form at the back of Saints' pack.

Despite their seeming control of the game, it was Biarritz, through Julien Peyrelongue, who scored the first of the afternoon's four tries.

Paul Grayson had earlier got a penalty but that lead was wiped out as Serge Betsen sliced the ball through Saints' defence and Peyrelongue won an ugly scramble to the ball.

Nick Beal put the visitors back in front two minutes later as some quick passing caught out their French opponents.

Oriel Ripol tore through Biarritz's defence and the ball eventually came for Beal after some slick distribution by Dawson.

Beal repelled two tacklers for the five points in the far right-hand corner and Grayson hit an impressive conversion to take the lead to 10-7.

The scores were level at half-time following a Betsen penalty.

But it was Northampton who come out the more focused after the interval.

And a Mark Connors try, comfortably converted by Grayson, early on put his side into a 17-10 lead.

Grayson's penalty 10 minutes from time put Saints 10 points clear and looked to be enough for victory before Yachvili converted his own try.

With Northampton's defence momentarily asleep, the former Gloucester player eased his way in for a try.

Yachvili capped a scintillating win with the match-winning penalty.

Biarritz: Brusque, Bernat-Salles, Stcherbina, Isaac, Bidabe, Peyrelongue, Yachvili, Menieu, Gonzales, Avril, Couzinet, Roumat, Betsen, Milheres, T. Lievremont.
Replacements: Fitzgerald, Campo, Puleoto, Tonita, Chouchan, Mazas, Bousses.

Northampton: Beal, Sleightholme, Cohen, Tucker, Ripol, Grayson, Dawson, Stewart, Budgen, Morris, Williams, Connors, Blowers, Pountney, Soden.
Replacements: Miles, Smith, Phillips, Seely, Howard, Hyndman, Brooks.

Referee: Alain Rolland (Ireland)