Pompey made it back-to-back wins in the Sky Bet Championship for the first time this season after coming away from south London with all three points for the second time this week.

It was enough to lift them six points clear of the relegation zone with this success plus Tuesday night’s at Charlton doubling their tally of away wins in the league.

It was not long ago that Portsmouth were still a soft touch on their travels, with a 5-0 drubbing at Bristol City on New Year’s Day something Mousinho considers a turning point.

Mousinho said: “Prior to the new year, we put in a half-decent performance at Derby and we were okay at Swansea, and then obviously at Bristol City we got blown away.

“But after that I think the way that we knuckled down post-Arsenal [in the FA Cup] – I know we lost the Arsenal game, but we were excellent on the day – we’ve replicated those performances away from home.

“I think it’s come from a reset after Bristol City, and a recognition of the fact that we can do both sides of the game pretty well when we put our minds to it.

“To come here, against the third best team in the league, we’ve watched them time and time again be a very impressive side, home and away from home.

“They’ve got threats all over the pitch, so to do that today off the back of Tuesday was really pleasing. I thought we were excellent throughout.”

Gustavo Caballero broke through for Pompey 19 seconds into the second half when he squeezed in from a narrow angle.

Some good work down the left by Millenic Alli then led to the visitors doubling their lead when his pull-back was thumped in by John Swift.

Casper De Norre bent in a lovely effort to get Millwall back in the game, but Portsmouth quickly restored their two-goal cushion when Marlon Pack swept in.

Millwall boss Alex Neil said: “I don’t think we deserved anything from the game.

“People will think when I say how we defended that I’m talking about the back four, but I’m talking about the whole team.

“This is a collective thing in that the first goal from our point of view was really disappointing.

“The second goal was equally as disappointing because we’re actually ‘intact’ – the first ball comes up, they nod it down, they win the second ball and work it round the corner, and we tried to nick from the wrong side and let them roll away from us.

“I said to the lads after the game that we’re built as a team on doing the basics really well and I didn’t think we did the basics well enough today.

“When the ball did go forward, it didn’t stick enough for us when we got it there and I didn’t think we won enough duels.”