After spending 27 years with the UK's elite SAS, TV star Mark "Billy" Billingham worked as a bodyguard for some of the world's biggest A-listers – including actor Tom Cruise and model Kate Moss – before becoming a permanent fixture with former lovebirds Brad Pitt and Angelina Jolie and their six children.
"The biggest concern for them was the kidnapping of the kids, it's all about money," the 53-year-old said of his 18 months working alongside the famous couple.
"Angie and Brad are very worried about who goes near the children."
But beyond the glitz and glam of guarding Tinseltown's most loved, Billy's work has involved some scary moments including terrifying run-ins with terrorists and capturing an IRA sniper using himself as bait, which saw the TV star and author awarded the Queen's Commendation for Bravery.
Now, he's starring on Aussie reality series SAS Australia, which see's him giving some of the country's most loved stars a run for their money as they compete in challenges set out for those in the real SAS.
Woman's Day caught up with Mark to learn if there's a softer side to his tough exterior.
Woman's Day:You've had an incredible career, from serving for almost three decades in the SAS to fighting in Iraq. What's one memory you have from being on the frontline that you'll never forget?
Mark: One day I'll never forget, it's actually a moment I will never forget, was when a hostage that we rescued saw daylight [again]. He had been held in captivity for a number of months and had been kept in the dark for so long – too long. It reminded me why we fight so hard for freedom.
You've met some very famous faces in your time, including the Queen. What was that like?
I had met the Queen prior to being awarded my Order of the British Empire. It was more a proud moment for my mum and dad who had no idea why I was receiving the award until the citation was being read out as I marched towards Her Majesty.
Aussie fans are so excited to know the series is returning next year. What sort of warning or advice would you have for celebs coming on the show?
I hope they get the chance to peel back the layers and truly find out who they really are and become a better person for that. The best advice I have for new recruits would be don't be put off and give it a go... this will totally change your life for the better!
This season has not been without its drama. Firass Dirani has caused a storm of controversy after suggesting things had been edited unfavourably and lashing out at other recruits. Do you think he was a bad fit for the SAS selection process?
I actually don't believe Firass cast a cloud over the show. I believe he had some good content because he was different. He stood by his guns – he was arrogant but that's what we needed for us to solve and highlight a few issues that needed to be sorted and also to create some animosity amongst the group.
Beyond your work on the frontline, you worked with Brad Pitt and Angelina Jolie. What was it like working with such big stars?
Working with such high-profile celebrities was great. I learned a lot of lessons from them, they learned a lot from me and the beauty of working together was the mutual respect. They respected what I had to do and I respected what they had to do, and it worked fine and created a very professional understanding.
What's one thing that surprised you about the Jolie-Pitts during your time working with them?
The one thing that surprised me about working with A-list celebrities, in particular Brad and Angelina, was their time management and how they had time to do everything from family life to work and to charity.
WATCH: Gone rogue! Firass Dirani critiques his SAS Australia co-stars on Instagram: