The mammoth trek to Cumbria appeared to be taking its toll on Pompey during a lethargic opener against Carlisle.
But the League One leaders gradually began to take control before dominating the contest following the interval.
And they made their pressure count when Abu Kamara came off the bench and threaded a pass through for Paddy Lane to stroke home the winner.
The scorer admitted that the Blues had been under-par and was delighted that the large travelling army were eventually sent home happy.
Lane said: “We were sloppy for the first 25 minutes before growing into the game and then came out for the second half all guns blazing.
“We’re all very honest with each other and knew that we hadn’t met the standards we set for ourselves.
"It’s unbelievable that they’ve made that trip up and packed out the away end, so I’m delighted for them."
“The gaffer got into us and you could see the response – we managed to get the goal to send the travelling fans home happy.
“It’s unbelievable that they’ve made that trip up and packed out the away end, so I’m delighted for them.
“It was great to see Abu come on and change the game like that – I can’t thank him enough for the pass.
“The journey back will be a happy one, but we have to remain focused and be ready to go again on Tuesday.”
Lane’s neat finish took his personal goal tally to 10 for the campaign – the first time he has reached double figures.
He said: “It’s not something I pictured at the start of the season and I just want to keep going as long as I can.
“I don’t set myself targets, but the more goals I score, the more games we’ll win and the closer we get to promotion.”