The outstanding Aiden O'Brien, who seems to just get better with every game, had a chance in the opening quarter of an hour when he ran at the Derby defence but fired a tame shot straight at goalkeeper Lee Grant despite having Gregory and Jimmy Abdou as options on either flank.

Two minutes later the visitors went close when a long throw by Ryan Shotton found Richard Keogh, but the captain's header drifted inches wide.

Millwall kept pressing with O'Brien testing Grant in the visiting goal from the edge of the box, whuilst the young striker had the ball nicked off his toes as he was about to pull the trigger following a superb pass from Nicky Bailey.

The Lions' pressure finally told in the 26th-minute when Gregory capitalised on a poor clearance from Grant that reached the edge of the box and although his angled drive was heading goalwards, Craig Forsyth had an opportunity to clear but seemed to slice the ball backwards and into his own net.

There was no doubting the scorer of Millwall's second, however, when Gregory clinically despatched a penalty beyond Grant's reach after Martin's cross from an O'Brien flick-on was handled by Keogh. 

Roared on by the home fans, Millwall had the bit between their teeth and sent over a succession of teasing crosses that Derby did well to defend. 

However the visitors were handed a lifeline three minutes before half-time when Sid Nelson gave away a cheap freekick 20 yards out with a tug of Conor Sammon's shirt. Up stepped Ince - of often Millwall's nemesis - to curl a shot beyond the reach of David Forde and into the bottom left corner.

Millwall - and Gregory - took just five minutes of the second-half to restore that two-goal lead. This time Hendrick was penalised for holding Dunne as Martin sent over a corner and referee David Coote pointed to the spot again. Gregory made no mistake for a second time, securing his first ever Football League hat-trick. 

The former AFC Halifax frontman, like strike partner O'Brien, worked himself into the ground and his hat-trick was a just reward for his effort.

Derby brought on top scorer Martin for Dawkins and within six minutes of his introduction, the sub had pulled a goal back with the third penalty of the game. This time, O'Brien's soft challenge on Ince as he darted into the box darted into the box saw ref Coote point to the spot. Martin stepped up and halved the deficit to ensure a nervy final 20 minutes. 

The Rams had keeper Grant to thank for producing two stunning reflex saves, firstly to tip over O'Brien's 73rd-minute curler and then a header from Martyn Woolford just three minutes later as Millwall pushed forward again. 

But it was Derby who grabbed a late point with the goal of the game - Ince teed up Hendrick and he in turn hit a net-busting volley from the edge of the area to level up at 3-3. 

Millwall had a half-chance to nick all three points deep into injury-time when sub Ricardo Fuller, a 78th-minute replacement for hat-trick hero Gregory, used his power and strength to work a path towards goal, but a perfectly timed tackle from Keogh averted the danger as he prepared to shoot. 

The Lions rightly left the field to a standing ovation and regardless of the final position in the League table on 2nd May, the 'P' factor - pride, passion and purpose - is back. 

Millwall: Forde, Dunne, Harding, Abdou, Nelson, Hooiveld, Martin (Gueye, 90mins), Bailey, Gregory (Fuller, 78mins), O'Brien (Cowan-Hall 90+2mins), Woolford. Subs not used: Archer, Powell, Thompson, Taylor-Fletcher.