Aberdonians were treated yesterday to a Gavin Hamilton century in all but name. The Scotland batsman's kit mysteriously vanished from the Mannofield dressing room on Tuesday night, forcing Hamilton to bear the name of Fraser Watts on his back as he guided Scotland to a five-wicket victory over Ireland with a commanding 115.

The former England left-hander from Broxburn led the Scots' pursuit of a target of 211 with considerable élan, passing 50 for the first time since February 2007 after facing just 52 balls, and then sparring his way to three figures. He had already given the locals something to cherish with an extraordinary catch to remove Andrew White in an Irish innings that saw two one-day international records achieved in the field.

Dewald Nel bettered Majid Haq's landmark bowling figures of 4-28 against West Indies with a return of 4-25, while local favourite Colin Smith scooped up another individual accolade for his four catches. As much as this was Hamilton's day, and a good one for Scotland, it was a personal shocker for Ryan Watson, who dropped a catch, saw another spilt by Qasim Sheikh off his own bowling and fell for a duck.

Watson also left his captaincy open to criticism when he chose to give Nel – who boasted figures of 8-4-17-3 from his first spell – only one more over at the end of the innings. But it's a mark of Scotland's improving outlook that they can win a game with 15 balls to spare without relying on their talisman, and his record suggests he is likely to be back on form today against New Zealand.

This was a deeply satisfying win for Scotland, as much for Celtic bragging rights as for their world rankings outlook. Victory over the marauding Black Caps, however unlikely a proposition that may be, would now transplant them onto the main table of the ODI rankings.

"They are about the best side going around in the world right now, but you never say never," said Hamilton, whose brand-new apparel seemed to have been thrown out by cleaners because he hadn't been around the night before to remove it from the manufacturers' packaging, which resembles a bin liner.

"Obviously it's now in a dustbin in Aberdeen somewhere, but I'm not that bothered now - I think I'm going to wear Fraser's stuff in future.

"It's nice to beat Ireland as they are ranked above us, and we were positive from ball one. That's the way we are playing our cricket at the moment. At the start of the year the bowlers were pretty much holding us together, but now we are gelling as a side."

The 33-year-old, winning his 75th cap, drove the first ball of Scotland's reply through extra cover and ran four after a misfield. The loss of Watson, driving to mid-off, didn't discourage him and he added 70 with Sheikh, who made 23 on his ODI debut, and another 122 with Smith to make the run chase an unusually becalming experience.

It was a completely assured display from a man out of professional cricket now for nearly three years. Ireland, as previously publicised, are missing a whole team and had only three experienced players carrying the Tricolour in Aberdeen, and their attack looks worryingly blunt. But none of them bowled badly yesterday; Hamilton's timing was spot-on and his punched drives were out of the top drawer.

Spin, introduced in the form of McCallan in the 12th over, caused the Scots to adjust their pace but Hamilton met Gary Kidd with the deftest of late cuts that raced up the hill for four. It was one of seven boundaries in his first 50, and another five would follow. Sixteen months after the World Cup meltdown that had critics calling for his head, here he is in champagne form.

Sheikh acted as a useful foil on his ODI debut, recognising the importance of restricting Ireland to one early breakthrough after Watson had driven Thinus Fourie straight to mid-off. One short ball from McCallan was swatted away through long-on by the Clydesdale youngster; the next one thudded straight to mid-wicket.

Smith looked vulnerable to lbw early on, and survived a huge appeal for a stumping by the impressive Gary Wilson, but he was determined to mark the occasion and was soon crashing the ball over the top. He was nicked out by Botha for 59, initiating a clatter of wickets that saw Watts charge at White and miss, but Richie Berrington got the three runs needed first ball.

Earlier, the excellent Nel and John Blain beat the bat repeatedly after the Irish won the toss, batted first and squirmed a little, and Ryan Haire's 54 led their recovery from the stupor of 65-4. They shouldn't have been allowed to reach 200 but for once, spin was a blunt weapon for the Scots as Glenn Rogers' radar wavered, and Kyle McCallan took full advantage for 39 from 38.

The Caledonian pace trio are in rare fettle and Gordon Goudie and Blain fully deserved their wickets, the latter benefiting from Hamilton's stunning one-handed catch, after an initial misjudgment, at deep square leg. This was Gav's day, even if most of the crowd thought they were watching someone else.