I went to the party to celebrate Vogue’s centenary (not the only one, I know).   Two things struck me.   The first was that it was founded in 1916, at the height of the first world war, when, as Nicholas Coleridge explained, there was both clothes rationing and paper rationing, not the most auspicious moment for the launch of a fashion magazine.   But British readers were apparently missing the shipment of American Vogue.   The second is the longevity of the Condé Nast stable.   Coleridge himself has been there for as long as I can remember (although he cut his teeth on Harper’s and Queen).   And Alex Shulman has been editor of Vogue for a quarter of its existence.