It would take an intrepid insect to elude the White House cleaning staff and sneak from the Oval Office, through the president’s study and set up camp on a gilded mirror that dominates the room. But if it could pull the escapade off, the creature would enjoy a grandstand view of one of the most intriguing social gatherings certainly of this year, arguably of the century. It is in this surprisingly pokey little room that George W Bush will host a unique lunch of all the living presidents — past, present and future. They number five: Bush himself, the incoming Barack Obama, and descending back into history, Bill Clinton, Daddy Bush and Jimmy Carter.

Such intimacy has never been achieved among presidents outside the inevitably dampening environment of the funeral setting. The Pittsburgh Post-Gazette’s description of the event as a “dejeuner for destiny” is perhaps a degree over the top, but it points in the right direction. The US presidency is the world’s most exclusive club, and the luncheon — apparently the brainchild of Bush himself as a means of helping Obama ease himself into the job — takes it to a new, literal level.

Sadly, we are likely to know next to nothing about their conversation unless we can debrief that fly. In the bland protocol of these things, we have only been told that the five men are likely to share anecdotes about life in the White Hou-se before discussing domestic and world affairs. There is plenty of opportunity for friction. Obama will surely know that it was in this very room, at a lunch between Bush and Dick Cheney in 2001, that they secretly agreed some of the most controversial measures of the “war on terror” — measures that Obama has vowed quickly to overturn.

Can the men steer around the subject of confronting Iran — and avoid reminding Carter of past failures? Or raising taxes — George “read my lips” Bush Sr likewise? Or interns - let’s not go there. And what about the seating plan? Is Obama, as guest of honour, to be put at the head of the table, or Bush, the man he so muchcondemned over two years of campaigning? And how can the younger Bush and Carter, who has been an irritant over the Mid-east, be separated? So many questions, in such a small space. Oh to be that fly.