It is remarkably easy to slay your demons when they turn up without a line-out.

Tonga were fiery, feisty and infuriatingly awkward opponents in the first half of yesterday's game against Scotland at Kilmarnock's Rugby Park, but when they were forced to the touchlines in the second everything went pear-shaped. Scotland scooped up their possession and ran away with the result.

Scotland coach Vern Cotter reckoned his players stole line-out ball six times in that period in their final Autumn Test. The best teams in the world would struggle against those statistics, and Tonga were not remotely in that category. Even without their profligacy in the set-piece, Scotland would probably have won with something to spare.

Not that you would have said so at half time. Up to that point, the Scots had struggled to get the better of the Tongan forwards - and the English referee JP Doyle - at the breakdown, where they were penalised heavily and often. Scotland captain Greig Laidlaw looked mystified at times - "there were a few tough calls in there, and maybe a couple of harsh ones along the way", was his diplomatic assessment afterwards - but his team never lost composure as they did when they were humiliated 21-15 by Tonga in Aberdeen two years ago.

Critically, when things weren't going Scotland's way, they knew how to change direction. Only later did we see the flamboyance and momentum that has characterised their play this autumn, but before they got to that point they had to show some hard-nosed pragmatism.

"It was a hard game, very tough," Cotter said. "Tonga put a lot of pressure on at ruck time and the penalties seemed to be going against us. The players simplified things in the second half and held on to the ball a bit more and tried to do simple things well. They got on top and managed to grind out an important win. Hats off to the boys. It wasn't an easy game. Tonga believed they could beat us again, so it was nice to take that away from them. It is hard to construct rugby against a team that plays as they do, but I thought our composure improved as the game went on. I think we can take confidence from that.

"I think the players are playing for each other, playing for the shirt and playing for people who come and watch them. That is really pleasing to see. The team have a soul and want to perform better and better."

They might have had soul, but there was little rhythm and a lot of blues in the way Scotland played in the first half hour. They managed to get an early try on the board, but the penalty count against them mounted quickly as Doyle pounced on every indiscretion and lack of urgency at the breakdown. It is a devilishly difficult job deciding how long a player can hang about the tackle area, but Doyle seemed to be of the opinion that a nanosecond just about covered it.

That helped Tonga fly-half Latiume Fosita collect 12 points with four penalties before the game was half an hour old, but even in that period Scotland showed glimpses of the sharpness near the line that would become much more evident later on, thrusting Blair Cowan over from a line-out drive for their opening try after 14 minutes.

Tonga had lost flanker and captain Nili Latu to the sin-bin in the build-up to that score, although they managed to take the lead while a man down. Soon after Latu's return, Alex Dunbar was shown the yellow card for a dangerous tackle on full-back Vungakoto Lilo, but the Scots matched Tonga by moving in front while short-handed.

That happened when Tonga had been pressing hard in the Scotland 22. Centre Siale Piutau rumbled round a ruck, but Finn Russell hit him hard from behind. The ball spilled free, and Stuart Hogg snatched it off the ground. A few seconds and 80 metres later, Hogg touched down at the other end of the pitch.

Laidlaw's conversion helped Scotland into a 14-12 half-time lead. At that point you could claim being in front flattered them, but that changed soon afterwards. Right from the off it was clear the second period was going to give us a very different game.

Scotland went from bish-bash to swish-swash, moving the ball purposefully and confidently across the field. They also kicked intelligently and well to pin Tonga in their own territory. From there, escape would have required a functioning line-out and the Tongans were a touch short in that department.

Dunbar collected the first of the Scots' second-half tries eight minutes in. Rob Harley made a trademark charge through the middle and Russell switched the direction cleverly behind the ensuing ruck. The fly-half whipped the ball to Dunbar, knowing that the centre was up against two forwards. To his credit, and probably relief, Dunbar beat both to touch down in the right corner.

That took Scotland to 19-12, but for all they were playing with momentum and self-belief, a couple of Laidlaw penalties soon afterwards were probably critical in establishing a lead that looked well nigh insurmountable.

Geoff Cross collected the fourth try with an improbable vault over a ruck on the line. Tommy Seymour then got the fifth - his third in consecutive games - after a fine cross-kick by Russell. Scotland walked off the plastic pitch a few minutes later with a noticeable spring in their steps.