Amal Clooney angered fashion designer Tom Ford's team after deciding at the last moment on a different look for the Met Gala.

The 40-year-old human rights lawyer decided just hours before the annual fashion event to arrive in her 'backup' outfit by British designer Richard Quinn, according to an article on Tuesday by PageSix.

She stunned in a strapless gown with silver bustier, dark slacks and a long floral train at least four feet long.

Backup outfit: Amal Clooney, shown last week at the Met Gala in New York City, reportedly wore her 'backup' outfit instead of her planned Tom Ford designed gown

Lady in red: Amal, shown with husband George Clooney, wore the Tom Ford custom gown to the after-party

PageSix reported that when Amal told Ford's team about the switch 'they were annoyed, obviously, but they were gracious, and and said it was fine to go with [another designer], but they would prefer that Amal not wear the dress at all if she wasn't going to wear it on the Met Ball red carpet'.

Fashion forces at Vogue also reportedly urged Amal to stick to the original plan.

Ford's people hoped that if Amal didn't debut the full-length crimson gown designed to look like a stained-glass window that another star would be able to at a future A-list function.

They were surprised and infuriated when Amal changed into the Tom Ford dress for the more private after-party.

Fashion designer: Tom Ford, shown in February in Beverly Hills, had his team working on Amal's gown, but she changed plans at the last moment

Vogue editor Anna Wintour, 68, who chairs the event said on The Late Show that Amal insisted on changing gowns inside the gift shop at the Metropolitan Museum of Art.

Amal was a co-chair of this year's Met Gala along with Rihanna and Donatella Versace and also appeared on the May cover of Vogue ahead of the gala.

There have been few designers more successful than Ford, who shot to fame back in 1994 when he was named creative director of Gucci.

The house was almost bankrupt at the time he took the reins, and within five years was valued at $4billion.

His edgy looks were a hit with critics as well, and in 1999 he took on a second job as creative director of Yves St. Laurent.

That post proved a bit more challenging at times for Ford, as even though critics loves his lines and profits for the fashion house were up, his work was hated by Yves himself, who was not shy about voicing his distaste for the young designer's hyper-sexualized aesthetic.

Then, in 2004, he walked away from the top post at both houses when questions began to arise about the future of Gucci group and who would be in control. He enjoyed a few years off before he launched his eponymous line in 2006, which included accessories and beauty products as well as his designs for men and women.

Cute couple: George escorted his lawyer wife to the Met Gala and the after party

Ford's womenswear line fast became a hit with A-list celebrities and high-society ladies, who had no problem dropping $11,000 on one of the designer's sequined gowns or a comparatively reasonable $2,200 for a black sleeveless dress.

Ford also did his best to make sure his designs were not overexposed, which may explain why he refused to dress Melania Trump back in the day.

The designer has made a point of never dressing more than one celebrity for major Hollywood events like the Oscars and Golden Globes.

Among those who have been lucky enough to walk the red carpet in a Tom Ford gown are Gwyneth Paltrow, Naomi Watts, Resse Witherspoon and Julianne Moore, who along with Tom Hanks' wife Rita Wilson has long been one of the designer's muses.

Ford is so strict about the one dress rule that Hayden Panettiere was forced to go out and drop $10,000 on one of the designer's gowns for the 2014 Golden Globes.

The actress, who was nominated that year for her work in Nashville, said that it had always been her dream to wear one of Ford's creations for a special night, but unfortunately for her the designer had styled Watts for the ceremony.

Ford did later send Panettiere flowers along with a note telling her how beautiful she looked that night.

Amal was accompanied by her actor husband George Clooney, 57, at the gala and after-party.

Amal and George welcomed twins Ella and Alexander in June 2017.

George can be seen in the upcoming TV miniseries Catch-22 based on the book of the same name by Joseph Heller.

He'll also be a producer and director of the miniseries also starring Christopher Abbott, Kyle Chandler and Hugh Laurie.

George was spotted on Tuesday filming in Italy.