The £50million man had not found the net for 901 minutes for club and country, 732 for the champions since joining them almost three months ago, but it took him just eight minutes to do so after coming off the bench today.
The jubilant Spaniard was mobbed by his team-mates after scoring in a victory that moved Chelsea back to within six points of Manchester United, with Frank Lampard and Florent Malouda also among the goals.
The margin of defeat was harsh on West Ham, who wasted several chances of their own as they ended the day back on the bottom of the table, two points from safety.
Amid all the talk of Chelsea's resurgence and West Ham's survival battle, the latest reunion between John Terry and Wayne Bridge had slipped under the radar.
Relations between the pair had not thawed in the year after allegations emerged about their private lives and Bridge duly snubbed Terry during the pre-match handshake, as he did last season.
The non-pleasantries were accompanied by a huge drop in temperature as the heavens opened after one of the hottest days of the year.
In what were admittedly treacherous conditions, Chelsea flattered to deceive in the first half, dominating the opening 20 minutes without finding the net.
Malouda looked certain to do so inside three minutes - just as he had done against Birmingham on Wednesday - but he shot straight at the onrushing Robert Green.
Didier Drogba, Ashley Cole and Malouda all went close but West Ham's blanket defence stood firm.
Their attacking threat had been virtually nil but that changed in the 24th minute when Petr Cech was forced into fingertip saves twice in a minute from Demba Ba's 30-yarder and Jonathan Spector's close-range header.
Drogba blazed over as the rain relented, only to be replaced by the sound of thunder, before the lively Freddie Sears was desperately unlucky not to Put West Ham ahead on the half-hour, his outrageous volleyed backheel from a corner cleared off the line by Cole.
Chelsea were becoming increasingly sloppy, with a suicidal Salomon Kalou pass going unpunished and a lack of communication seeing Cech take out team-mate David Luiz.
But with just a minute of the half remaining, Chelsea produced their best move of the match to take the lead, Drogba threading in Cole, whose low cross was smashed home by Lampard.
The rain returned and there also appeared to be a floodlight failure before the interval.
That was rectified during half-time, after which Kalou fired wide from 12 yards before John Obi Mikel blocked Da Costa's header from a corner.
Both sides lost men to injury moments later, Michael Essien hobbling off and Mark Noble carried off on a stretcher in worryingly innocuous fashion.
Drogba's free-kick just evaded Terry but his cross moments later should have been converted by Lampard, who scuffed straight at Green.
The pitch was in danger of becoming unplayable but David Luiz smashed a long-ranger against the crossbar moments before Ba's blockbuster was fumbled by Cech and Hammers substitute Robbie Keane shot straight at the keeper.
With 20 minutes remaining, Kalou was withdrawn for Anelka, with Torres made to wait by Ancelotti.
Keane really should have levelled 16 minutes from time when Spector's through ball left him with just Cech to beat but he blazed wide.
Ba became the latest player to clear off his own line before Torres replaced Drogba for the final 14 minutes, squaring for for Anelka to score what should have been the clincher, Danny Gabbidon heading off the line.
Then, the moment every Chelsea fan had been waiting for arrived.
Anelka's through ball played in Torres and the ball cruelly appeared to hold up in a puddle.
But that proved a blessing in disguise as the Spaniard swivelled and curled home left-footed.
Stamford Bridge erupted and every outfield Chelsea player piled on top of a jubilant Torres next to the corner flag.
The striker even played a part in Chelsea's stoppage-time third, which Malouda lashed into the roof of the net, a strike that could prove vital if goal difference comes into play in the title race.