Scotland 323 for 5 (Coezter 89, Berrington 56, Watts 54, Davey 50) beat Ireland 320 for 8 (Stirling 113, Cusack 71, Mommsen 3-26) by five wickets
Ireland were given a rude awakening by Scotland at the Grange, as their oldest rivals showed them that they can no longer rest on their laurels as No. 1 Associate nation.
Despite scoring their third-highest ODI score, Ireland slipped to a five-wicket defeat with nine balls to spare. It ended a run of seven limited-over wins in succession for Ireland over Scotland, and gave the latter the Celtic-nations bragging rights for now.
On an excellent batting pitch, Scotland made nonsense of the form book and history books as they chased 321 to win. Ireland's bowlers never found their length and were put to the sword by some breath-taking batting.
Richie Berrington's 56 off 23 balls was the final blow, but the opening stand of 129 between Kyle Coetzer (89) and Fraser Watts (54) set Scotland on their way as Boyd Rankin and Trent Johnston misfired.
It was quite a shock to most of the vibrant Edinburgh crowd, who had seen Paul Stirling's third century in four ODIs spur Ireland to a commanding 320 for 8 earlier. Stirling's thunderous innings of 113 was backed up by a typically-measured 71 by Alex Cusack and a breezy fifty by Andrew Poynter.
Stirling was perhaps stirred into belligerent style - his hundred came up in 83 balls - by a communication from his county. Middlesex told him to report to the second XI at the conclusion of this tournament, as his services would not be required this week by the first team.
Stirling was given every assistance by the home bowlers, who squandered the toss by bowling far too short and wide of the stumps. Scotland's raw opening bowler, Safyaan Sharif, saw a six and a four disappear off Stirling's bat over cover in his first over, before William Porterfield took consecutive boundaries off his third.
The Irish opening stand sailed past fifty in the ninth over, before a bowling change brought Scotland a breakthrough. Porterfield tried to hit Josh Davey over the top and instead skied to Coetzer at mid-on. Cusack joined Stirling, and settled into his favoured role of second fiddle.
Stirling raced to his fifty off 45 balls as the 100 was raised in 18.2 overs. Scotland skipper Gordon Drummond made frequent changes as bowler after bowler failed to quell Stirling and Cusack.
By the 22nd over he was on to his seventh bowler, Kyle Coetzer, but he was whipped out of the attack when his third over was plundered by Stirling. The second ball sailed into the crowd at extra cover, and three balls later he disappeared into the distance, the ball still rising as it flew over the wall surrounding the picturesque Grange ground.
Stirling raised his century off 83 balls in the 28th over, and had time for a sixth six before he fell to Majid Haq. In the absence of Niall O'Brien, Andrew Poynter took a rare chance to show his class, and pulled and swept powerfully while Cusack continued to accumulate.
Poynter's fifty came up in 33 balls. He perished at the hands of the eighth bowler Drummond used, South African-born Preston Mommsen. The innocuous-looking offspinner kept his lines tight and picked up 3 for 26 off five tidy overs. His second scalp was Kevin O'Brien, who was surprised by the bounce of the first ball he received, which he proceeded to steer into the diving, outstretched hand of Majid Haq at short third man.
The Irish lower middle order is well-practised in finishing an innings, and Gary Wilson and Trent Johnston ensured the total reached 320.
But some stirring batting from Scotland made the target look innocuous. Trent Johnston laboured hard, but his lack of match-practice told. In the last ten weeks he has bowled just 25 overs, all for Ireland, as he has been forbidden by Cricket Ireland from turning his arm over for his club Railway Union .
George Dockrelll ended the opening stand when Watts missed a sweep, but the Somerset youngster never settled and bowled his ten overs in five spells. Coetzer continued his purple patch, getting his fourth consecutive ODI half-century, and equalling his career-best score of 89, set two weeks ago against Netherlands. He fell to Rankin who got a pearler to take the top of off stump.
Berrington took up the baton however and a blistering batting Powerplay of 65 runs ensured victory was comfortably secured. He hit six sixes, most of them over the tennis courts into Arboretum Avenue.
Ireland coach Phil SImmons said he was "disappointed rather than angry" at his charges. "Its the sort of kick they need sometimes," he said. "They need to learn not to underestimate anybody.
"They did it last week against Namibia and got away with it. But today we lost intensity and its hard to get momentum back when that happens."
When Ireland beat England in Bangalore during the World Cup, they celebrated in the team hotel by singing "Are You Scotland in Disguise?" as they encountered the England players.
As the Scotland players celebrated in their dressing room last night, one wag was tempted to lead them in a chorus of "Are You England in Disguise?"