The Major Change Britney Spears Made After Ex Jason Alexander Trespassed at Her House

Jason Alexander trespassed at the singer's home on her wedding day.

Britney Spears made a major change after Jason Alexander trespassed at her home on her wedding day. A source tells ET that, after the incident ahead of Spears' wedding to Sam Asghari, the 40-year-old singer "fired her whole security team."

"Jason Alexander trying to crash their wedding was a complete disaster and no one understood how it could have possibly happened," the source says. "Britney felt that her security team was underprepared and she was very flustered and overwhelmed."

Alexander barged his way into Spears' Thousand Oaks, California, home on her wedding day, demanding to see Spears. He was tackled by security and ultimately arrested by Ventura County Sheriff's deputies responding to a trespassing call.

Following the incident, Spears was granted a three-year protective order against Alexander, whom she was briefly married to in 2004. Her ex has pleaded not guilty to the charges against him -- including felony stalking, misdemeanor trespassing and refusing to leave private property, misdemeanor vandalism-damage, and misdemeanor battery.

"Although there were some hiccups," the source says, alluding to the Alexander incident, "Britney and Sam had an amazing time at the end of the day."

"They are so beyond happy that they are married," the source adds. "They aren't going to be honeymooning just yet and they are just enjoying this moment together."

Among the guests at the nuptials were Madonna, who, according to the source, "gave Britney jewelry as a wedding present."

"Britney was so thrilled to have her there to celebrate, along with her other friends," the source says of the bride, who also welcomed the likes of Selena Gomez, Drew Barrymore and Paris Hilton.

Donatella Versace, who made Spears' wedding dress, was also on hand for the big day.

"Britney and Donatella have an extremely close relationship," the source says. "They are planning to have Britney sit front row at upcoming Versace shows and Britney wants to do more with the brand going forward."

Aside from living in newlywed bliss, the source says that "Britney is also working on her tell-all book deal and is hoping to have her book come out soon." Spears, whose $15 million tell-all book deal was revealed in February, is expected to write about her conservatorship in the memoir, after the more than decade-long legal arrangement was terminated in November.

"The book is going deep," the source says. "She is sharing all details and not holding anything back. She wants to share her full side of the story and everything she went through."