Kydd receives the congratulations after his winning try

Saints, battling to avoid relegation, were given no chance in San Sebastien but won 7-6 courtesy of Kydd's try.

"Everyone wrote us off coming here but we showed today there's no reason why we can't win it," said the centre.

"We play Wasps now and we've beaten them once this year already so there's no reason we can't do it again."

Saints trailed 6-0 with 12 minutes left when Kydd pounced on a loose pass from Dimitri Yachvili to race 70m to the line, Carlos Spencer converting for a lead the visitors held on to in a frantic finish.

"I felt like I was going up and down on the same spot," Kydd added of his try. "Fortunately Carlos did some good blocking for me - it must be his NFL training!

It proves that on any given day, sport can turn up some bizarre results Saints coach Paul Grayson

"It's an amazing feeling to win here. I think the 22 players and the management were the only ones who thought we could do anything.

"But we have shown what we can achieve when things go our way."

Northampton coach Paul Grayson admitted his side had gone into the match with damage limitation at the front of their minds.

"I think we were 100-1 in a two-horse race - quite big odds, but that's what sport is all about," he said.

"In the big picture, we didn't really think about getting a win because on paper, Biarritz should have won.

"We wanted to frustrate them and keep the score close, because you never know when you are going to get something like an intercept to turn the game.

"What summed it up for me was when they tried a drop-goal at the death and half a dozen Saints players charged forward - they still had that desire.

"It has been an incredible week, and an even more incredible day.

I'm disappointed, angry and frustrated Biarritz coach Patrice Lagisquet

"We've got a massive game away to Newcastle, but right now, we don't even want to think about that.

"We have made the Heineken Cup semi-finals against all the odds. It proves that on any given day, sport can turn up some bizarre results."

Saints will face Wasps in the semi-finals at Coventry City's Ricoh Arena on 22 April, a week after facing the same opponents in a Premiership encounter crucial to their survival hopes.

Biarritz coach Patrice Lagisquet admitted his side only had themselves to blame after their shock defeat.

"I'm disappointed, angry and frustrated. Going into the game, there was no way could I see Northampton beating us," he said.

"We dominated the set-pieces and I was disappointed with a couple of refereeing decisions in the last minutes. Northampton did what they had to do and we should have closed the game down and got the job done.

"At half-time, I said we had to be patient and put away our chances, but we didn't do it."