The club was celebrating its 100th anniversary, and thanks to a superb two-legged play-off semi-final win over Cardiff City had booked the first trip to the Twin Towers in its long history.
Swansea City, who were managed by former Liverpool and Denmark midfielder Jan Molby, lay in wait under a hot London sun - with 32,000 Cobblers supporters having made the trip south to cheer on their heroes.
The Swans had twice beaten the Cobblers in Nationwide League Division Three that season, but it was to be a case of third time lucky for Ian Atkins and his team as they wrote their names into club folklore.
The game was far from a classic and looked to be heading to extra-time as the clock ticked past 90 minutes and the teams still locked at 0-0.
But striker Christian Lee was fouled on the edge of the penalty area to offer up the Cobblers one last shooting chance - or two chanes as it turned out!
John Frain took the initial free-kick, but it was charged down by Swansea's Jonathan Coates who had broken away from the wall.
Referee Terry Helibron ordered a retake, popped the ball down - in a slightly different place - and the rest is history.
One perfect swing of Frain's left peg sent the ball curling towards the left-hand corner, goalkeeper Roger Freestone couldn't get there, and it was game over.
Cue a massive hour-long party for the players, staff and the army of fans at the tunnel end of the old Wembley Stadium.
From the Chron archives, here are the memories of some of the key men from that famous day, starting with, who else, but goal star Frain...
Free-kick hero John Frain
"The game itself was a pretty steady game from a spectacle point of view.
"Playing in it, you don't really think about whether it is a good game or not because it's such a tense moment and you're caught up in it.
"When we got to 90 minutes I bracing myself for extra-time.
"We got a free-kick on the edge of the box and I can't remember what happened or who got fouled.
"It was on the right hand side of the box and I was on set-pieces at the time so I had a crack.
"It was so late in the game and it was quite a good chance to score, but for the first effort by the time I hit it one of their players had broken out of the wall and he was less than five yards away from me.
"Fair play to the referee, he ordered for it to be retaken and I think the ball was slightly moved, so it was more central.
"It wasn't a massive difference but it opened up both sides of the goal.
"The first one I could only hit to the keeper's left but the movement changed that.
"I just concentrated on hitting the target and getting a good strike on it.
"From then on, things seemed to go in slow motion. You know straight away if you have got a good strike on the ball.
"The way I hit it, it felt nice and it seemed to be in slow motion until it hit the back of the net.
"That was an amazing feeling, one I've never experienced in football.
"There was a whole range of emotions.
"It took everything out of me and I was just pleased there wasn't any extra-time, because it was difficult to get your head back on the game and concentrate.
"The whistle went 30 seconds later and again that was an amazing feeling.
"People come out with all the old cliches, but they're all true.
"You practice in the back garden for years as a kid and then to do it at Wembley, which was the place to play at as a footballer then, was very special.
"You dream about that sort of thing, scoring the winning goal in the last minute of a cup final at Wembley."Full-backs rarely get the chance for those things to happen though, and I was really privileged to have that happen to me."
"The game was actually pretty drab and I can mainly remember the build-up for it.
"We had a cracking week. A band who had made a record for the occasion came down to the ground and they did a video and photoshoot there, it was quite an exciting time.
"We had suits from Marks & Spencer and shows from Church's, all the perks that went with getting to Wembley.
"Whoever had those contacts at the club did us proud because it was just like the build up to a cup final.
"I was lucky enough to be part of the Sunderland squad when they got to the FA Cup Final in 1992 and it was very much along the same lines as that.
"To win at somewhere like Wembley, especially if you've had bad times in the past, perhaps do make it that bit more special.
"It was a great achievement for the club at the time, especially with what they had been through before with the money troubles and finishing bottom of the league.
"We had a good set of players and we knew exactly how we had to play every time we went out there."
"It was probably the highlight of my career to play at Wembley with Northampton.
"I got there with Gillingham as well but I didn't play that time so I experienced both sides of it.
"I've got two main memories of the game and the first one was being told I was going to be playing that morning.
"The other one is Frainy scoring and the final whistle going straight after, that was it.
"That's pretty much all I can remember from the match, it wasn't a classic!
"I didn't think we would have much of a chance from the free-kick when I got fouled, because I had seen Frainy's free-kicks all season!
"I thought it was just going to go to extra-time, but he pulled one out of the bag.
"It was a great goal and obviously one I'll never forget, but I wasn't expecting it and I don't think anyone else was either!"
"The goal and the celebrations afterwards are the things that most stick in your mind. The game came and went that quickly.
"Going around the ground afterwards and being with all of the fans was very special.
"We could have stayed out there all night to be honest.
"The game probably wasn't the greatest spectacle, but to finish it in that manner, with Frainy popping up with the winner and the timing of it, it couldn't have been any better."
The gaffer - Ian Atkins
"We were only getting 5,000 at home that season and then we took 32,000 to Wembley!
"Some of those people had never seen us play before.
"The town was always known for the rugby, but that day put Northampton on the map for the football.
"I was fortunate enough to win a championship medal at Everton and we did the open top bus tour around Liverpool after that.
"But the city had seen it all before and it was spasmodic all the way round. In Northampton it was incredible.
"The whole thing was just a fantastic two weeks and it's something I'll never forget and will always cherish."