The former England player, a second-half substitute, claimed Birmingham's first league goal in 380 minutes, enough to fire them to their first away win of the season and ruin English football's only 100 per cent home record.
Suddenly, Liverpool's presence at the upper end of the table seems less convincing, while Birmingham's position is substantially more comforting for their manager, Steve Bruce.
Those who have followed Liverpool's season from close quarters will tell you that this was an accident waiting to happen. Whatever they had planned for the January transfer window, they must now have no doubts that at least one new striker has to be their priority.
Djibril Cisse's appalling long-term injury and Milan Baros's hamstring strain left them with two stand-in strikers, Florent Sinama-Pongolle and Harry Kewell, who made scant impression on a Birmingham side who had managed just one previous win in the Premiership this season.
Kewell was loudly derided by the gallery as he toiled to pose a genuine threat and Sinama-Pongolle was withdrawn midway through the second half.
Birmingham, too, were underpowered in attack. They had only one out-and-out striker, former Liverpool player Emile Heskey, and he has palpably not become a predator overnight.
Birmingham would have been content with a point yet must have sensed early in the match that all three were within their compass, given a rare break.
The dearth of specialist goalscorers was soon evident. John Arne Riise, a scorer in each of Liverpool's last two Premiership fixtures, met Luis Garcia's centre with a glancing header that floated beyond the far post.
Kewell carried the ball from deep until it occurred to him he should shoot. He generated enough power to force a parry from Maik Taylor. Xabi Alonso's tame offering made life easier for the goalkeeper. Heskey might have made an early impact on his return to Anfield but could not apply the required deft flick to Muzzy Izzet's near-post cross.
Izzet was more culpable still after 15 minutes as he found himself beyond Liverpool's back line. He failed to capitalise and instead took a knock as Chris Kirkland won the duel. Garcia then spurned Liverpool's most glaring opportunity of the half, blazing over from barely eight yards.
Julian Gray, a constant source of menace, went on another slalom that almost took him through the entire Liverpool defence. Dietmar Hamann was presumably as surprised as Birmingham's defence to find himself trundling down an uncluttered path to goal. His finish, alas, was more predictable and Taylor saved.
The goalkeeper had Izzet to thank for keeping his goal intact after 71 minutes. The midfield player twice cleared off the line from his station by a post.
Liverpool's angst was compounded five minutes later, when Birmingham went ahead. Robbie Savage swung the ball high to the far post, Matthew Upson headed back across the face of goal, and Anderton stabbed the ball in from close range to secure Birmingham's first win here since 1978.