A top UK Government official called for Celtic and Rangers to play a special friendly match in Belfast to mark the signing of the Good Friday Agreement, released Cabinet documents show.
Alastair Campbell wrote to then prime minister Tony Blair to raise the idea in April 1998 and suggested the two Glasgow clubs could wear each other's jerseys as a gesture of conciliation.
The former Downing Street director of communications, whose parents hailed from Scotland, said he had a "direct in" with Celtic while he could get Manchester United manager Alex Ferguson to approach Rangers.
"Both in terms of raising publicity for the campaign and in sending out a message, it would be very powerful," the Cabinet memo said.
In the letter headed 'Rangers v Celtic, An Idea', addressed to Prime Minister, Tony Blair, Northern Ireland Secretary Mo Mowlam and Scottish Secretary Donald Dewar and dated 12 April 1998, Campbell asked if the idea was worth pursuing.
There is no record of anyone getting back to him.
Campbell tweeted today: "Perhaps not the best idea I ever had."
The Good Friday Agreement was signed on April 10, 1998 after intense negotiations between the UK Government, the Irish Government and Northern Ireland political parties.
It marked the end of the Troubles and led to the creation of the Northern Irish Assembly at Stormont.
But the agreement was also controversial as it led to the early release of paramilitary prisoners who had been jailed in Northern Ireland.
It was viewed as a key success of Labour's early years in power after the party won a landslide victory at the 1997 General Election.
Campbell was once one of the most feared media spinners in British politics before stepping down in 2003.
His father, Donald, was a Gaelic-speaking vet who grew up on the island of Tiree before later moving to Yorkshire for work.
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