Rebecca Tyrrel: Anna Wintour's loathing of calories is as well-documented as her rudeness

Who knew that Anna Wintour, hotly tipped as the next US ambassador to the Court of St James, or possibly Paris, never says "Goodbye" at the end of a phone call? In The Devil Wears Prada, the Wintour character played by Meryl Streep concluded chats with a clipped and faintly brusque, "That's all".

The actual editor of American Vogue, British born and bred but now a US citizen, simply hangs up when she feels the discussion is over. "There's no point, is there, really?" she once explained. "We've finished talking."

This natural warmth was perhaps best summed up by Barbara Amiel, who said: "Anna happens to be a friend of mine, a fact which is of absolutely no help in coping with the cold panic that grips me whenever we meet."

If Obama does reward the leading fundraiser with a glittering embassy after next month's inauguration, Wintour is not expected to spoil guests to the Regent's Park or Parisian residence with the Ferrero Rocher. Not unless they produce a bespoke chocolate free of sugar, cocoa butter and, oh yes, chocolate. Her loathing of calories (she advised Oprah to lose weight before appearing on the cover of Vogue) is as well-documented as the glacial rudeness.

There are other apparent drawbacks to her taking a job whose primary function is to use suave chit-chat to put people at their ease at nightly social events. She never stays at a party longer than 20 minutes (her bedtime is a rigid 10.15pm), doesn't do small talk, and delights in putting everyone at their unease.

Yet she does have impressive form in the field of smoothing troublesome international relations. Her most celebrated edition carried a famously flattering profile of the al-Assads, Syria's first family, in which Asma opened the door herself, "hair in a ponytail, the word 'happiness' spelt out across the back of her T-shirt"; and the dictator revealed that he chose ophthalmology for his medical speciality because "there is very little blood". (Wintour later changed her tune somewhat, issuing a statement "deploring the actions of the Assad regime".)

What a novel experience for president Obama it will be if and when he does make that call: "Forgive me, Anna, they want me in the Situation Room – something to do with Syria and chemical weapons. But let me just say how thrilled I am that you've accepted the… Anna? Are you there? Hello? Madam Ambassador? What is wrong with this phone? Anna? ANNA?"