All of this is an excuse for the stars to perform, with varying degrees of skill, the greatest hits of Abba, some of which, regrettably, do not survive the disfigurement.

NEWYORKER: Mamma Mia!

But - just to confirm that not all of Tony Blair's greatest hits have gone out of fashion, he gave his enthusiastic backing to the euro - a sound that has not been heard since, well, Lord Mandelson was last in government.

BBC: Brown unity show with Blairites