Instead this was a victory for the 13th ranked side in world cricket and made a mockery of the International Cricket Council's decision to stage just a 10-team World Cup without the Scots in England next year.
It will be a huge concern to England a year before they host the World Cup that their attack could look so toothless and concede so many against an associate team full of club players.
England may have been missing Ben Stokes and Chris Woakes but there was a worrying lack of penetration while their bowlers were not skilful enough to contain the Scots on a surface that offered them nothing.
It became the first time in any one-day international that four England bowlers had gone for more than 70 runs apiece, with seam and spin alike providing little threat.
Plunkett, left out by Yorkshire last week from their 50-over team, may have taken two wickets but he was the most expensive while Mark Wood struggled for the pace that once set him apart and Adil Rashid too often pitched short.
That should take nothing away from a Scotland side still bristling from their desperately unlucky failure to qualify for the World Cup and eager to prove they belong at cricket's top table. How they proved a point on Sunday.
None more so than MacLeod, 29, who was simply superb in racing to three figures off 70 balls to become the first Scot to score a hundred against England and inspire his side to their highest score in any 50-over international.
This is a cricketer who once played for Warwickshire and Durham but had to stop bowling because of a suspect action and has most recently been plying his trade for Hampshire's second XI and for Bexley in Kent.
Here he looked completely at home against the best one-day side in the world, slog sweeping Moeen Ali for six to reach 50 and clearing the short Grange boundaries twice more while also hitting 16 fours.
There were also half centuries for the Scottish captain Kyle Coetzer and a left-handed hitter in George Munsey who bamboozled England's spinners with his reverse sweeping on his way to 55.
The only possible criticism that can be levelled at Scotland is their failure to score even more as, at 200 for three after 30 overs, they should have been aiming at getting even nearer to 400 than their eventual 371 for five.
It looked as if it would not nearly be enough when Bairstow set off like a train, going to 50 off 27 balls with 16 off three balls from Michael Leask and then looking sure to make the quickest hundred in England's one-day history.
Bairstow fell slightly short of that but he still became the first Englishman to hit three successive one-day hundreds when he reached the fastest of his five 50-over centuries all made since September, this one off 54 balls.
Even though Bairstow was to depart for 105 England were still cruising when they reached 220 for two in the 27th over but a catalogue of errors sparked by the needless run out of Joe Root was to prove England's demise.
Root spread his hands out in dismay when Alex Hales called him through for a single that was never on and Hales compounded his error when he fell immediately after captain Eoin Morgan cutting carelessly to point.
When Sam Billings, wasting a rare opportunity to impress with England, hit a full toss from Mark Watt straight to mid-wicket four England wickets had fallen for 43 and the big upset was on. Another in David Willey quickly followed.
It did not like it would be for Scotland when Moeen and Plunkett were adding 71 for the eighth wicket but Moeen senselessly threw it away before Rashid then ran himself out. Wood was trapped lbw by Safyaan Sharif and cue jubilant scenes for Scotland's first ever victory over England.
And to think this was meant to be a warm-up. England now move on to play Australia in five one-day matches. It cannot possibly be any tougher than this.
