On the ground where he played senior cricket, in front of a handful of spectators, as a 13-year-old, the Irishman took centre stage with almost 10,000 people watching to finish 124 not out, winning the match with his fourth six.
Morgan, still six days short of his 27th birthday, shared a world record fifth wicket partnership of 226 with Ravi Bopara who deservedly reached his century before England chased down their victory target of 270 with an almost ridiculous seven overs to spare.
And Morgan wasn't the only Irishman in red yesterday. Boyd Rankin, after 38 ODIs for Ireland, was given his debut and was England's most successful bowler, taking four for 47 as Ireland were restricted to 269 for seven.
William Porterfield dominated that innings, the captain scoring his 10th century for Ireland but his first in an ODI for three years, since his 115 against Bangladesh at Stormont, still Ireland's only victory over a Full Member on home soil.
It was a welcome return to form for the opening batsman who has lost his place in the Warwickshire four-day line-up but his international statistics this year stand up with the best of them - this was his second hundred to add to four 50s in 10 innings.
Boyd Rankin took four wickets
But for the second big match in row, Porterfield was let down by his bowlers. In May, Pakistan were 133 for seven, chasing 240, and they won by two wickets; yesterday, thanks to Tim Murtagh's impressive opening spell, Bopara came to the middle with England struggling on 48 for four.
It was to be another 204 runs before Ireland got another chance - and Niall O'Brien, without gloves, on the deep mid-wicket boundary spilled it. Five balls later it all over.
Morgan finished 124 not out, his fifth one-day century - six if you include the one for Ireland against Canada in 2007 - from just 106 balls with eight fours and four sixes. Bopara was even quicker, facing 75 balls and hitting 15 boundaries, five of them clearing the fence.
Porterfield insisted on giving his medium pacers, Kevin O'Brien and John Mooney, seven overs in the middle of the innings - two of them in the powerplay overs - and, as he admitted later, "in hindsight it was probably the wrong move".
Huge six from William Porterfield brings up his hundred
Max Sorensen, left stranded after three overs as first change bowler, was not recalled until Ireland were just 25 runs from victory and his extra pace conceded just seven runs in his solitary over. The medium pacers conceded 68 in their seven overs. But, then, even George Dockrell could not stop the runs haemorrhaging, the slow left armer conceding 73 runs in his most expensive 10 overs for Ireland.
Rankin was one of three England debutants but it was not such a good day for the others. Gary Ballance was out second ball - although he did hold the catch to dismiss Paul Stirling, in the same over as he crashed two fours through the covers - while Michael Carberry put down two catches, including Porterfield on 85, and was the butt of the crowd jeers throughout the day.
Four overs later, Ed Joyce stepped back on his stumps and was given out hit wicket, but only after Rankin had pointed out the missing bail to the umpires who had to refer it to the television umpire.
Tim Murtagh
James Tredwell, getting big turn, picked up of the wickets of Niall O'Brien and Gary Wilson, although the latter was unlucky as the ball hit him outside the line, and when Kevin O'Brien was brilliantly held by Eoin Morgan at mid-wicket, Ireland were in trouble at 161 for five.
But John Mooney, the victim of another umpiring error, saw Porterfield to his hundred, which he brought up with a huge six, off Rankin, into the stands at mid-wicket.
In all, the Ireland captain faced 143 balls and also hit 14 fours and when he was out at the start of the 46th over, Sorensen, on his ODI debut scored 24 off 17 balls and with the help of Trent Johnston, Ireland added 45 in the last five overs to give the record crowd a chance of witnessing another famous victory.
After 15 overs they were dreaming, but 28 overs later it had turned into a nightmare.