The man known variously as the Prince of Darkness, Sultan of Spin or plain Minister Sinister let his mask slip once more as he reminisced about his grandfather and Dome predecessor, former Labour statesman Herbert Morrison.
On his first Dome-related duty since becoming a cabinet minister last week, the Secretary of State for Trade and Industry wallowed in family nostalgia when he opened a new exhibition in London on the1951 Festival of Britain and its Dome of Discovery.
The Festival, which was his grandfather's grand idea to put a smile on the face of a nation wearied by postwar austerity, had inspired his own efforts to make the Millennium Dome a success, he said.
Surrounded by Greenwich museum's display of faded Double Diamond beer mats, Festival headscarves, jigsaw puzzles, radiograms and cigarette cases, the Minister for the Future lost himself in a 1950s haze, flicking mentally through his family album.
"He described it as `a gesture of faith in a brighter future'. I think that captures the '51 Festival and, you know something," Mr Mandelson said, his voice cracking. "That's exactly the same spirit that's going to capture the Millennium Experience in the Dome."
A self-confessed "grandfather's grandson", he said the presence of the man who masterminded the Festival while carrying out his duties as Atlee's Foreign Secretary, cast a shadow over his work on the Dome.
"If he's up there, somewhere, my old granddad," he went on, clearly moved, "looking down with his one eye, with that great steely look, that firm grip, that iron will, for which he was famous, he would be looking down and saying, `It had better be as good as '51'.
"I feel him hovering over my efforts. Now, you realise why I'm a little nervous. You realise why the Millennium Experience could be a little career- shrinking if it goes wrong. But it won't."
Long before was he was elevated to his present "proper job", stewardship of the Dome was Mr Mandelson's first concrete (not to say Teflon and steel) project and he begged the Prime Minister to let him keep it under his control.
He said that it was "incredible" just how similar his experience had been to that of his grandfather, with the Festival of Britain criticised by both Labour and Tory MPs as a waste of public funds.
"I was speaking to my mother, who is very much alive, about her memories of '51 and what he had to go through. The Left called it an extravagance, a great indulgence by my grandfather. The Tory Right felt as though they owned Britain's past. The Left and the Right try again and again to defeat the hard-working majority."
To anyone who has seen Mr Mandelson at his most ruthless, it was an eerie sight.
Or, to use his own prediction of a day out at the Dome in 2000, "an absolutely unforgettable experience".Reuse content