For a good chunk of the first half here in the east end, it looked like the Celtic players would have rather had this game called off. While Morton’s high command had voiced their concerns about this William Hill Scottish Cup tussle going ahead in the wake of the wide spread meteorological misery during the week, the Greenock players on the park did their bit to issue something of a red warning alert to their hosts as a spirited, sturdy showing from the visitors left the cup holders huffing and puffing through a dogged opening 45 minutes.

Celtic had the kind of possession that could have roused the interest of the drug squad but it took a double-whammy from Moussa Dembele in a nine minute spell just after the hour to crack Morton’s robust resistance. The second half introduction of Odsonne Edouard, who would gild the lily in the last minute, made a sizeable difference to the Celtic cause as Brendan Rodgers’ team moved up through the gears. A slightly contentious penalty award which allowed the home side to double their lead on 71 minutes may have been hard on Jim Duffy’s troops but, as the Morton manager conceded, the quality in the Celtic ranks shone through in the end.

With Rangers looming on the horizon next weekend, the impact of Edouard and Dembele’s continued resurgence has been timely for Celtic.

“Moussa has got that hunger back to score and in the second half, like the rest of the team, he was much better,” said Rodgers. "And I thought Odsonne was very good. I've an idea of what we want to do if everyone's fit next week but certainly today he (Edouard) provided the spark the team needed.”

Rodgers felt the lack of training due to the snow was a factor in his side’s sluggish start. Spare a thought for Morton, though. “We had a half hour training session in a blizzard at Battery Park on Friday,” said Duffy of life at the other end of football's pecking order. “The goalie coach Davie Wylie got the shovels out and cleared a 20-yard area for us. It got us a touch of the ball but the snow was blowing all over the place. That's all we did since Tuesday.”

For this grand day out in this cherished old event, Morton could not have looked more Scottish. Striding out in a red tartan away kit, they could have been accompanied by the drum major of the Lower Clyde Pipe Band.

The Green Brigade’s constant clattering provided a thumping soundtrack but the Greenock brigade were determined to march to the beat of their own drum. They even had the temerity to ask Celtic to switch ends after the toss of the coin.

Within moments of things getting underway, they had the Celtic defence in a fankle. Marvin Compper’s first touch on his debut was pretty dicey as his wayward pass trundled across dangerous territory. It was pounced upon by Gary Oliver but instead of having a strike he opted to drive into the area and the opportunity was snuffed out. “It was a bumpy start for me,” admitted Compper.

It was an early lift for the Morton morale, though. Gary Harkins, with his canny, considered approach, certainly seemed to be enjoying himself as he ambled about the acreage of the Celtic Park turf and his free-kick from distance and another raking effort generated a few excited oohs and ahhs among the travelling supporters.

In between that activity, Celtic came within a whisker of a breakthrough when Dembele’s looping header was nodded off the line by Thomas O’Ware.

For all their meanders forward, Celtic had barely got Derek Gaston, the Morton keeper, warmed up but he had to look lively as half-time loomed. Tom Rogic’s powerful shot was turned round the post before the Australian had a searing volley beaten away.

Edouard had an early chance to make an impression after the resumption but scuffed a shot at Gaston before an opener finally arrived on 62 minutes. Rogic’s nicely floated cross saw Dembele take flight and his header bounced in off the bar. Nine minutes later, Dembele surged towards the area and was sent sprawling by Michael Boyle’s lunge. It was a close one to call but that particular call went in Celtic’s favour and Dembele plonked the spot kick high into the net.

"I've seen it on the camera and you're always happy to get them,” admitted Rodgers. “At the time, I thought it was a penalty but when you analyse it, we are all experts when we watch it five times.”

Gaston thwarted Dembele’s assault on a hat-trick with a flying save but Edouard finally notched a third in the dying embers. A terrific pass from Scott Brown breached the Morton rearguard and sent James Forrest scampering away and his cross was eventually converted from close range.

“Celtic grew into it as you'd expect then changed their personnel and system in the second half,” added Duffy. “They have umpteen players with class. That class told in the end."