For 90 minutes, we were conned. Birmingham City and Aston Villa put on such an admirable show of sobriety that we were duped into believing that it was a normal Premiership match.
And then, out of nowhere, appeared Lee Hendrie.
As the final whistle confirmed a 2-0 victory for Birmingham, the Villa midfield player seemed to declare war on everybody who was not Lee Hendrie, providing us with a reminder that these matches are less about football than human emotion.
One could understand Hendrie's distress. Villa had failed again at St Andrew's and, despite enjoying much possession, showed that they have learnt little in 21/2 years about what is required in the midst of such intense rivalry.
Apparently, Hendrie's reaction was borne of frustration after Mario Melchiot, the Birmingham right back, ended the match with what might euphemistically be described as an exercise in showboating.
Hendrie took offence, a scuffle broke out, and the acrimony continued in the players' tunnel. It was nothing significant - the referee, Mike Riley, will not even mention it in his report - but it emphasised the perception that the real beauty of derbies is in their belligerence.
Thomas Sorensen would probably disagree. The Villa goalkeeper, whose mistake allowed Birmingham to take a fortuitous one-goal lead, lives in hope that these matches were like any other.
If they were, his error would have been forgotten. In the context of a Birmingham-Villa match, it was another matter. After Sorensen allowed a shot by Emile Heskey to trickle under his body and into the goal, the Birmingham supporters expressed their gratefulness with typical sardonic wit.
To the tune of Nice One Cyril, they sang: "Nice one, Tommy; nice one, son; nice one, Tommy; let's have another one."
That is one problem of these matches. The external attention acts like a microscope, exaggerating every mistake and every good deed.
Sorensen has suffered twice now, just as Peter Enckelman suffered twice for mistakes during the 2002-03 season. Olof Mellberg suffered for ill chosen words prior to the derby last December but he restored some personal pride yesterday, even if he did find Emile Heskey difficult with which to deal.
Heskey turned in yet another display of international quality, suggesting that, at £6.25 million, he is proving to be a bargain signing. True, Heskey's shot from which Birmingham took the lead should not have registered a goal, but the striker deserved a goal for a perfect display of unselfishness.
The battle between Heskey and Mellberg was a worthy subplot to the main feature. Both are colossal figures, both have international pedigree, and both have that rare ability to rise to an occasion.
This was a big occasion, so they were bound to play significant roles.
Mellberg's performance seemed to resemble that of his beard. He started slowly but, with Heskey tiring, improved as time went on. By the end of the match, Mellberg was looking like Karl Marx.
But it was Heskey who was smiling.
Villa's problem was not at the heart of the defence, where Mellberg and Martin Laursen performed well, it was in the full-back positions, where Jlloyd Samuel and Ulises de la Cruz were below acceptable standards.
This was essentially the difference between the teams. There were no weak links in the Birmingham team but there were plenty in the Villa team. Whereas Sorensen made that crucial error, Maik Taylor made three impressive saves for Birmingham. Whereas Samuel and de la Cruz were struggling, Jamie Clapham and Melchiot were stable and confident.
David O'Leary's formation of 4-5-1 was designed to ensure that Villa controlled the midfield but it could hardly be described as a success. Indeed, midway through the second half, Villa went to 4-4-2 but hardly benefited.
It was not their day. Even the free kick by Nolberto Solano in the first half was tipped on to the far post by Maik Taylor. Late on, in one incident, Taylor twice saved at point-blank range when Villa seemed to have enough chances to have won an entire tournament.
The impression is growing that Villa are not geared towards these matches. Their style of play does not flourish in such circumstances and their players, though talented, perhaps prefer more moderate environments.
The surprise, of course, is that, in Lee Hendrie, Villa have the one player who seems to embody everything that Birmingham want in a player.
He works hard, he is emotional, and he adapts well to different situations. He is - or should be - Villa's equivalent of Robbie Savage. Alas for Villa, Hendrie did not come close to stamping his authority in midfield.
It was Stephen Clemence and Darren Carter, rather than Hendrie and Mathieu Berson, who looked more in tune with the requirements of this match.
Perhaps that was another reason for Hendrie ' s frustration at the end. His love for Villa is never more obvious than in moments of sorrow and pain. When Villa are losing, he takes it personally.
The problem with these derbies as far as he is concerned is that Villa lose a lot of them. That is four defeats and two draws in six matches, a run of form that is starting to surprise even the Birmingham supporters.
"Easy, easy," they sang as they filed out of St Andrew's.
It is not easy, of course; it is just the way the Birmingham players make it look. The paradox is that it takes blood, sweat and tears to conceal the effort.
Birmingham have mastered that. Villa have not. Yet.