Spurs, their supporters believed, were on their way to Wembley and until the last 10 minutes of this match, so it seemed. Having had a considerable majority of possession, the Londoners were looking comfortable when Gareth Bale put them ahead halfway through the second half.

It was then, however, that manager André Villas-Boas, as he often does, made an essentially defensive change, sending on Jan Vertonghen for Tom Carroll, and not for the first time this season, it backfired spectacularly. While the Belgian defender could hardly be blamed for inadvertently deflecting Alex Tettey's shot into his own goal, the teams' momentum had already begun to change.

Suddenly it was all Norwich, and Simeon Jackson then seized on Grant Holt's header to put Norwich ahead from close range. It is worth noting that Tettey, Jackson and Holt were all attacking substitutions. Even then Spurs had a glorious chance to take the game into extra-time, but Clint Dempsey saw his 88th-minute penalty superbly saved by Norwich goalkeeper Mark Bunn, and the result is that Norwich are in the quarter-finals of this competition for the first time for 18 years.

Villas-Boas brushed aside suggestions that his negativity might have been a factor. "If I'd brought on attackers you can be punished in the same way. I put Jan into midfield, where he has experience playing, just to give a little bit more freshness and to equal Norwich's height, because we anticipated they would bring on Holt.

"It's a pity to see the game slip from our hands and we're disappointed. When it comes to conceding late goals we have to do better: it's something in our mind and we are working on it."

In beating Arsenal and having the best of a draw at Aston Villa in their previous two games, Norwich had shown they are capable of recreating the level of performance which kept them up last season. Whether they will go on to do so consistently remains to be seen, and in that respect Chris Hughton might almost have preferred to see his side play well and lose unluckily than play badly and scrape through; but the Norwich manager still made a full 10 changes.

Villas-Boas was relatively restrained, his seven alterations not necessarily those predicted. That Bale and Dempsey started suggested the Spurs manager was taking this competition rather more seriously than his predecessor. Under Harry Redknapp, Spurs had gone out at the first hurdle in the last two seasons.

Judging by the large number who had made the journey up from London, the Spurs supporters clearly shared the Portuguese's opinion, and they can only have been optimistic after a first half which, if disappointing in terms of the number of chances created, ended with their team very much on top.

The only semblance of a Norwich chance fell to Morison, or would have done if his lack of pace running on to Andrew Surman's through-ball had not allowed Kyle Walker time to get back and make the tackle.

Bale, first turning Jake Livermore's low cross just wide, and soon afterwards shooting into the side-netting, went closest to scoring, and the second half was following a similar pattern until the Wales flyer was allowed to run across the front of the Norwich penalty area before firing a low right-footed drive inside Bunn's right-hand post.

Then came the substitutions. Vertonghen's presence did make a difference, but not in the way Villas-Boas had hoped. With Tettey's shot going outside the post, the Belgian instinctively put out a foot and deflected it past Hugo Lloris in the Tottenham goal.

The excitement was just beginning. Two minutes later Holt won a header and Jackson, having seen his initial shot blocked by Lloris, prodded the rebound home. Even then Spurs had the perfect chance to equalise but Bunn dived to his left to block Dempsey's firmly struck penalty, given for Marc Tierney's foul on Walker.

"Sometimes you need a little fortune, and the first goal was clearly a deflection, but we haven't had one of those all season," said Hughton. "As for the substitutions, sometimes you have to try and force the issue, and it had been a cagey game until they scored. I just wanted to bring a little energy into our game. "