Former Derby striker Rob Earnshaw inked himself indelibly into Forest folklore as his current employers completed a first League double over their East Midlands rivals since 1990 and shortened their odds for a promotion challenge.
The 29-year-old Welshman, who switched allegiance with a £2.65 million transfer in 2008, supplemented his two goals in Derby's 5-2 humiliation at the City Ground in December with yesterday's winner, 11 minutes from time.
Earnshaw, who had spent the first 65 minutes on the bench, earned a yellow card for celebrating in the away fans' section after providing former Derby manager Billy Davies with his first Pride Park victory since taking charge at Forest.
On a bobbly pitch in blustery conditions, Forest's counter-attacking had yielded few chances as Derby, with new signing Ben Davies prominent, revealed some character after eight defeats in 10 matches including an FA Cup loss to non-League Crawley Town. But when Nathan Tyson, often the most dangerous attacker, broke down the left and found Paul Anderson with a deep cross, his fellow wide man knocked the ball back for Earnshaw to beat Stephen Bywater with a right-foot shot from 20 yards.
The best chance up to that point had fallen to Derby in the first half, when Miles Addison hurried Wes Morgan into a mistake but Chris Porter fluffed the opportunity.
The result might further test the resolve of Derby's board after pledging their faith in Nigel Clough's management but there was no sign of cracks in the home crowd's support and any barracking came from the Forest fans, who taunted their former favourite with chants of "non-League Nigel".
Yet Clough was upbeat. "We missed the outstanding chance and their one shot in the second half ends up in the bottom corner," he said. "That's the way it is going for us at the moment."
Derby's captain Robbie Savage, who expects this to be his last "big match" in English football with a move to the United States in the offing, was substituted, in his manager's words, to "avoid a red card" after following a booking with more fouls. Full-back Dean Moxey was not so lucky, dismissed in stoppage time for a second yellow.