But after a far-post poacher's header in the 33rd minute to complete his first league hat-trick, and only the second of his nine-season career, Smith said: "I've apologised to Jayson. I said sorry.

"I said to him that his celebration probably merited the goal. But it came so quickly, I just stuck a leg out and it's just hit the top of my foot.

"I knew instantly it had come off me, and also I knew Sky were watching and they were going to see it in close up, so I didn't have any concern in my head it was mine."

Smith's only other hat-trick came just over five years ago when he scored all four goals in a 4-2 Johnstone's Paint Trophy win at Gillingham while with Bristol City.

"I've been in the division long enough, so it was about time one came along," added Smith. "I've had plenty of twos over the years but to get a three is no easy feat. I'm happy to see it happen."

The win was Millwall's largest away from home in the Championship since a 4-1 triumph in November 2012, with Forest again the victims.

Rowett said: "I'm really pleased after the last couple of performances in which we've maybe not done enough to win the game.

"I spoke to the players about it, that if they wanted any sort of opportunity in pushing for the top six then we had to grasp the game, be a little braver than we have been, and we were.

"And defensively I thought we were absolutely superb, as we have been all season, and conceding the least number of goals since I've come in (in October)."

Forest had the chance to move to within five points of the top two with a win, but their own promotion hopes are faltering after claiming just six points from the last 18 on offer.

Boss Sabri Lamouchi blamed the loss on tiredness. He said: "We gave them the opportunity to kill us, and they killed us.

"It was a classic plan to play on the counter-attack and we suffered a lot. It's a bad moment for us and we showed our limits physically and mentally. It was the wrong performance and a bad result."