Brad Pitt angelina jolie children body guard
Hollywood actors Brad Pitt (R) and actress Angelina Jolie (2nd L) arrive with their children Knox (2nd R), Vivienne (blocked) and Pax (front L) at Haneda international airport in Tokyo July 28, 2013. Pitt flew into Japan on Sunday to attend promotional events for his movie "World War Z". Reuters/Issei Kato

Guarding Brad Pitt, Angelina Jolie and their six children was the toughest mission to date for Mark Billingham especially as it included fathering the celebrity kids.

A former Special Air Service (SAS) agent of the British Army, Billingham claimed that he was one of the couple’s few staff members who were allowed to get near Maddox, Pax, Zahara, Shiloh, Knox and Vivienne while he served as the head of security of the Pitt-Jolie household for 18 months.

“I was Brad and Angelina’s head of security. The military set me up perfectly for what I did with them,” Billingham told The Sun. He is now a celebrity himself as he stars on the UK reality show “SAS: Who Dares Wins.”

According to Billingham, Pitt and Jolie are very much concerned about the safety of their children.

“Angie and Brad are very worried about who goes near their children.

“It was clear from the start we had a great chemistry and they trusted me with the kids. We got very close, I was living with them all the time.”

Brangelina divorce

The estranged couple is now battling over legal custody of the children after Jolie sought court clearance in September to be divorced from Pitt, whom she married in August 2014. (Read: Angelina Jolie pulls the plug on Brangelina, files for divorce from Brad Pitt)

But during his stint at the Pitt-Jolie household, Billingham claimed the couple trusted him with their children.

“I could take the kids anywhere I wanted to on my own. No one else was allowed to do that,” Billingham added.

“Even when I wanted to bring in extra people, they wouldn’t let any of those near the kids. They could look out for them from a distance but they couldn’t physically touch them. I took them swimming. I fathered them, basically.”

Angelina Jolie Brad Pitt with security
Mark Billington (bottom) is seen with Angelina Jolie and Brad Pitt during the 60th Cannes Film Festival in May 21, 2007. Reuters/John Schults

He shared details of a recent trip Jolie made to Iraq for the United Nations.

“She recently went into Iraq for the UN and I looked after her beforehand, got her ready for it and looked after Maddox when she went in.”

But apart from keeping the children’s safety, Billingham said he also had to protect their social image by carrying spare clothes in case the kids stained their attires.

“I had to make sure their image was protected, that they were dressed properly and not doing silly things that could be caught on camera.”

A father-of-six himself, Billingham said the time he spent with the the Jolie-Pitt children kept him away from his own.

“In 17 months I was only home for six weeks,” he admitted. “It was just too full-on. I never had a private life. I was exhausted. I lost direction in my own family life.”

Before working for Pitt and Jolie, Billingham has also looked after Hollywood A-listers including Tom Cruise, Rusell Crowe, Sean Penn and Kate Moss.

Billingham has since returned to the UK. He is now part of Channel 4’s “SAS: Who Dares Wins.” He joins the reality show as a new instructor alongside Anthony Middleton, Jason Fox and Matthew Ollerton, who will guide 25 civilians through an SAS selection test in the Ecuadorian jungle. “SAS: Who Dares Wins” airs in the UK on Channel 4.