The game’s first decent chance fell Boro’s way when Marvin Johnson fired in an inviting low cross from the left. Any touch would have been enough, but it was just out of the reach of Britt Assombalonga.

Paddy McNair then whipped in another quality ball from the opposite flank. Boro’s no.9 got to this one, and it was only a smart block from Jake Cooper that denied his effort.

Boro grew in confidence as the first half wore on. McNair delivered a third hopeful cross that was just over the head of Dael Fry, before a clever flick from Ashley Fletcher sent first Assombalonga then Djed Spence away. Spence appeared to beat Murray Wallace on the outside before coming crashing to the ground in the penalty area, but the referee waved play on.

Spence turned provider with yet another teasing ball in that had just too much on it Ashley Fletcher, then the lively McNair arrowed a powerful drive from a teed-up free-kick that tested the reflexes of Bartosz Bialkowski in the Lions goal.

Within a minute of the restart, Boro went agonisingly close again, McNair sweeping over from just inside the box after a smart pull-back from Fletcher.

Gary Rowett made three substitutions and changed shape for the home side, who soon carved out their first real opportunity. Matt Smith got across George Friend as the ball came in, and forced an excellent one-handed save from Dejan Stojanovic. 

The Boro keeper was called into action minutes later as substitute Connor Mahoney drove for goal, Stojanovic saving with his legs this time. 

Millwall were in the ascendancy, but it would be Boro who made the breakthrough on the counter. Ashley Fletcher worked the channels and broke free of his marker, carrying the ball a long stretch before squaring and providing a simple tap-in for Britt Assombalonga.

As the hosts pushed for an equaliser, Boro punished them again. Fletcher was presented with a one-on-one opportunity by Jonny Howson’s through-ball, but was grounded before he could get his shot away by Cooper. The Boro man stepped up to finish emphatically and secure a vital three points.