Marlon Harewood was never likely to be given a friendly welcome on his return to the City Ground, even without helping to nudge his former club another defeat closer to a relegation struggle.
The lanky striker, who moved to Upton Park after turning down a new contract offer exactly a month ago, needed only six minutes and 16 seconds to make himself the least popular man in Nottingham by slotting home West Ham's opening goal.
When Jermain Defoe added a second for Alan Pardew's side six minutes from the end, Harewood's old team-mates were contemplating the alarming possibility of a battle to keep out of the Second Division only 12 months after getting a sniff of the Premiership.
Forest, who were play-off semi-finalists last season, have gone 10 matches without victory since winning at Bradford on 25 October, and the gap between themselves and the bottom three has become perilously narrow.
West Ham's form of late has hardly been startling, but a third win in 13 matches since Pardew took charge promises to revitalise their promotion challenge, although yesterday's victory had a downside in that it might have been the much-coveted Defoe's last appearance in a claret and blue shirt.
The England Under-21 striker is about to begin a five-match suspension following his dismissal against Walsall nine days ago and may have switched clubs by the time the ban is completed, with either Manchester United or Chelsea thought likely to bid for him when the transfer window opens on Thursday.
Forest fear predatory interest from similar sources for their Republic of Ireland midfielder Andy Reid, and another sparkling display from the winger yesterday will only have encouraged potential suitors. Reid was at the heart of almost every Forest move yesterday but even his impressive contribution could not deny West Ham a comfortable win.
The Forest manager, Paul Hart, admitted last night that the club's financial situation made them vulnerable unless the chairman, Nigel Doughty, could provide the cash to make selling a player unnecessary.
"The simple fact is that while we remain a First Division club we lose money and that gap has to be bridged, either through sales or through the chairman's intervention," Hart said.
Reid's form was a plus point for Hart, who also had praise for the debutant midfielder Ross Gardner, the 18-year-old former Newcastle player, but in truth only some top-class saves from the goalkeeper, Darren Ward, spared Forest a heavier defeat.
The Welshman brilliantly kept out goal-bound efforts by Defoe and Hayden Mullins in the first half before defying David Connolly and then the substitute Kevin Horlock in the second.
But he could do nothing to stop Harewood sliding in to give West Ham their early advantage after Defoe had headed on a Matthew Etherington cross. Harewood, snapped up for a bargain £500,000 after scoring 12 First Division goals for Forest, wisely declined to celebrate his fourth in his new colours with more than a handshake or two as the majority of a 27,000 crowd digested a moment they had dreaded.
Ward had no chance either when Tomas Repka's long clearance set up Defoe's 10th goal of the season, the striker easily turning inside a tiring Michael Dawson to blast home from close range.
Pardew said it was the most satisfying West Ham performance since he took charge. "We have been lacking consistency but that was as good a 90 minutes as I have seen so far," he said. "Apart from the moments when Reid had the ball I thought we were always in control."
He said he hoped that Defoe, whose suspension is subject to an appeal which will be heard today, would remain at West Ham. "Like 14 clubs in the Premiership we are vulnerable to the spending power of the richest, but I've told Jermain I think he can go to the European Championship next summer as a West Ham player," Pardew said.
Goals: Harewood (6) 0-1; Defoe (83) 0-2.
Nottingham Forest (4-1-3-2): Ward; Louis-Jean, Dawson, Thompson, Doig; Williams; Reid, Stewart (Jess, 80), Gardner; King, Taylor. Substitutes not used: Roche (gk), Sonner, Gunnarsson, Robertson.
West Ham United (4-3-3): James; Stockdale (Ferdinand, 90), Pearce, Repka, Quinn; Carrick, Mullins, Etherington; Connolly (Horlock, 67), Defoe, Harewood. Substitutes not used: Hutchison, Bywater (gk), Mellor.
Referee: R Beeby.
Bookings: Forest: Taylor, Louis-Jean.
Man of the match: Reid.