Mark Billingham spent 27 years in the SAS, fought in Iraq and won the Queen's Commendation for Bravery after capturing an IRA sniper by using himself as bait, The Sun reports.
However, his toughest job was not on the battlefield, but it was guarding estranged Hollywood couple Brad Pitt and Angelina Jolie.
Mark, also known by his nickname Billy, was the eyes and ears for 18 months. As a result, he developed a close relationship with the children and reckoned he was their unofficial father.
Currently, he is entering the world of showbiz as a new instructor for Channel 4's SAS: "Who Dares Wins", which is back tonight.
He is joined by Anthony Middleton, Jason Fox and Matthew Ollerton to put 25 civilians through an SAS selection test in the Ecuadorian jungle.
He claims that it is not for the faint-hearted and Brad Pitt should not apply.
Billy, 51, says: "Brad wouldn't last long, because he wouldn't have any cream to put on his face. It would be too sweaty and uncomfortable for him. He's too pretty! But Angie could do it. She'd probably be the only one with balls at the end. She would stick it out."
Billy, who is also an MBE, was signed by Channel 4 after being impressed with his credentials.
His depth of experience also gave him the opportunity to work for Brangelina.
Billy shares: "I was Brad and Angelina's head of security. The military set me up perfectly for what I did with them.
"The biggest concern for them was the kidnapping of the kids, it's all about money."
He revealed that that the couple were extremely focused on protecting their six children - Maddox, 15, Pax, 12, Zahara, 11, Shiloh, 10, and twins Vivienne and Knox, 8.
According to Daily Mail, Billy said that Pitt and Jolie trusted him with their children so much that as he bonded with them, he 'could take the kids anywhere he wanted on his own'.
He also shared how the former power couple were consistently uneasy about who would go near their children, to the extent that they were mindful of security professionals.
Lastly, Billy spent so much time around the children, he said he felt like he "fathered them, basically."