In front of a sell-out crowd, Craig Bryson's 5th minute goal put Derby in front but the Reds had gradually gained a foothold in the game when the same player burst through, catching marker Guy Moussi napping, to make it two just after the half hour.
And the Rams all but made the game safe when they caught Forest on the counter attack for Hendrick to score on 36 minutes, the second time that a goal had come just seconds after the visitors had been on the attack themselves.
Moussi had been off the pace throughout the first-half, one misplaced pass earning the wrath of teammate Jara, and he was hauled off at the break with Darius Henderson given the task of rescuing something from the day for the Reds.
Things quickly got worse, however, when Johnny Russell netted a fourth inside ten minutes of the restart and a rampant Derby gave Bryson the chance to complete his hat-trick from the penalty spot when the impressive Bamford was fouled in the penalty area.
Both Reading and Brighton have the chance to overtake Forest in the table with draws in their 3pm kick-offs and cap a very bad day for Billy Davies side with the Scot himself now set to come under serious scrutiny as promotion hopes start to look very ambitious indeed.