The couple ended their two-year marriage on Friday at a court hearing in London which lasted around a minute.
Amanda, 31, who is 38 years younger than Bryan, filed for divorce from the former Roxy Music frontman, citing his continuing unreasonable behaviour as the reason for their split.
The former PR executive also confirmed she was no longer living in the couple's West Sussex home after her friends claimed that Bryan "acted like a child".
"Amanda hoped they could sort things out between themselves and keep it low-profile," a pal told The Express. "But Bryan's behaviour towards her means that she no longer thinks this is an option.
"He has acted like a child," they added. "She packed up her things and he made a point that she couldn't take some basic items."
Amanda first met Geordie singer Bryan after previously dating one of his four sons and the couple were married at the Amanyara luxury beach resort on the Turks and Caicos Islands in 2011.
"I'm very fortunate that I work in music, where you're in touch with different age groups," said Bryan before the wedding. "Either the audience or people you work with.
"Obviously I'm not ageist!" He added. "I have a young girlfriend but I don't like to talk about it. It just seems perfectly natural to me."
Bryan has previously been in relationships with Jerry Hall, Lady Emily Compton and Katie Turner and was married to model and socialite Lucy Helmore, with whom he has four sons, Otis, Isaac, Tara and Merlin.