Cheltenham Town's impressive form on their travels continued with this comfortable win at Scunthorpe United.
All the damage was done in the first when goals by Sam Smith and Callum Wright put daylight between themselves and United at the break.
The hosts though were brighter in the second half and created a handful of chances to force their way back into the contest but once again the Robins were well organised to restrict their opponents, thanks in part to some good saves by Josh Griffiths.
They remain unbeaten on the road this year and this victory was their fourth in four from February, a maximum haul on the road and a run in which they have only conceded one goal.
Duff hailed his side's performance after the game. "I'm really pleased today," he said
"I thought it was s clinical, profesional performance and we got the two goals relatively early.
"We knew we had to be good to win here because they've won four in five going into this one, and three of them were here so it was always going to be tough.
"In the second half we were quite prepared to sit in and see the game out.
"There were a couple of moments when we could have played some better, free flowing football but if you look at some of our away performances this year, when we've played other teams off the park but not won, it's about mentality.
"In the end it was as comfortable as it can be in this league."
Duff made two changes to the side that came away from Cambridge in midweek with a hard fought win.
Charlie Raglan returned after injuring his back ahead of that match at the Abbey Stadium, while Callum Wright was handed his second start after his debut at Walsall.
Lewis Freestone and George Lloyd dropped to the bench as Duff restored the 3-5-2 formation after using four in midfield four days ago.
Smith forced the first meaningful save of the game after 18 minutes, racing on to a ball by Matt Blair before cutting inside and releasing a low shot from an angle down the right. Mark Howard, the Scunthorpe goalkeeper, pushed it into the path of Wright before producing a low save to deny the striker with the follow-up.
The Reading loanee drew another stop midway through the half before he finally made the breakthrough with 25 minutes played.
It came about after some fantastic play down the right by Blair, who chased a ball to the byline before cutting it back to find Smith, volleying home from 12 yards.
Wright then made it two after his side had turned defence into attack four minutes before the interval. Blair carried it forward down the right and switched it out to Chris Hussey, who sent it in low to the feet of the Leicester City loanee. He took a touch, spun and found the net with a smart finish for his second goal for the club.
Then Finn Azaz almost made it three, but his glancing effort found the side netting.
The Robins were indebted to Josh Griffiths for a pair of fine stops to deny Kevin van Veen and Devarn Green to ensure his side carried their two-goal cushion into the second period.
The home side responded positively after the break and gave the Robins defence more to think about, but not for the first time in recent weeks they showed plenty of resilience.
Scunthorpe went on to produce a couple of good chances, the first of which arrived 23 minutes from time, Kevin van Veen with a devilish free-kick from 22 yards. Griffiths, though, was equal to it.
Then Manny Onariase, who spent two loan spells under Gary Johnson at Whaddon Road, headed against the bar after Griffiths missed a Mason O'Malley corner from the right.
But Cheltenham saw it out to complete a perfect run of results in February.
SCUNTHORPE UNITED (4-4-2): Howard; Clarke (c), McGahey, Taft (Onariase 7), O'Malley; Gilliead, Karacan (Beestin 61), Spence, Green; van Veen (Hallam 77), Loft (Eisa 46). Subs not used: Watson (Gk), Brown, Rowe.
CHELTENHAM TOWN (3-5-2): Griffiths; Raglan, Tozer (c), Long; Blair, Thomas, Azaz, Wright (Vassilev 65), Hussey; May (Lloyd 65), Smith (Williams 79). Subs not used: Flinders (Gk), Freestone, Horton, Chamberlain.
REFEREE: C Pollard