Anna Wintour has “total control” over the Met Gala guest list.

The Vogue editor-in-chief, 73, who has chaired or co-chaired the event since 1995, is also said to approve the “majority” of the outfits on show, according to the author of a newly-released biography on the journalist.

Writer Amy Odell, whose book ‘Anna: The Biography’ came out on 4 May, told Grazia when asked about how much influence Anna has over the annual Gala: “Total control. No one gets into the event unless she approves them.”

When asked if the editor approves dresses or seating plans, Amy said: “She approves the majority of the dresses, and might even review the sketches of the looks in advance.

“The seating plans are meticulously created. She often breaks up couples to force them to mingle with new people.

“She considers whether someone is an ex of someone else and might not want that person in their sight line.”

Despite her level of control, Amy said Anna loves off the wall looks, adding: “One friend told me that she loves the over-the-top looks! A lot of people have criticised the gala for becoming too much of a costume party versus a black-tie event.

“But Anna – who remember, is a huge theatre fan – enjoys the theatrics.

“The first time she left her spot inside the museum where she greets guests was for the Camp Gala – she went outside to watch Lady Gaga come up the steps (when the singer’s entrance involved choreography and several outfit changes.)”

Amy said when quizzed on whether they had been “any difficult guests or people she wouldn’t invite again”: “There have been incidents with guests. A former gala planner told me once she had a guest pass out in the bathroom. “Every year people smoke in the museum, which is not allowed – this has been the case for decades though it only recently became a news story.”

The journalist said about how Anna wants the Gala to be her “legacy”: “Anna has told friends she wants her legacy to be for her philanthropy.

“The Met Gala is the biggest philanthropic endeavour of her career, raising hundreds of millions of dollars for the Costume Institute at the Metropolitan Museum of Art. It is also, her friends told me, a fun night for her, even though it is also work.”