He has trained would-be assassins and marshalled invading hordes, Napoleonic forces and Roman regiments, but movie military adviser Paul Biddiss found himself in the midst of his biggest Hollywood skirmish last month when the actor Saoirse Ronan made a powerful intervention about women’s personal safety. Ronan, a guest on Graham Norton’s BBC chatshow sofa, sparked a nationwide debate about women’s security fears when she interrupted fellow actors as they discussed techniques that Biddiss had taught the casts of both Gladiator II and the new drama series The Day of the Jackal. Paul Mescal, who opens in cinemas this weekend in the lead role in Ridley Scott’s epic Gladiator sequel, swapped details of his new combat skills with Eddie Redmayne, star of the Sky Atlantic show based on Frederick Forsyth’s thriller, when Ronan unexpectedly made her intervention. Mescal asked: “Who’s actually going to think about that?” when discussing using his phone as a weapon, then Ronan pointed out that women do – they think about how to physically protect themselves daily. “That’s what girls have to think about all the time,” she said. “Am I right, ladies?” Within 24 hours, Ronan’s words had been repeated across the airwaves and social media thousands of times. “Saoirse was absolutely right,” said Biddiss, a Parachute Regiment veteran, this weekend, in his first interview since the viral incident. “It was a bit of a shock to suddenly be at the centre of such an important moment. Paul and Eddie were just enjoying a bit of banter about whether anyone would ever think to use their mobile phone as a weapon, as I’d suggested. “But, as Saoirse then said, phones, along with everything else inside a handbag, are always on the mind of a woman who is walking alone. All these items can be used, and particularly a mobile phone, which is carried in the hand a lot.” Redmayne, Mescal and his Gladiator co-star Denzel Washington, also a guest that night, accepted her intervention with good grace. Speaking this weekend on RTE’s The Late Late Show, Mescal backed Ronan’s view, saying: “Saoirse was spot on, hit the nail on the head, and it’s also good that ... messages like that are gaining traction, like that’s a conversation that we should absolutely be having on a daily basis.” The actor added that Ronan is “quite often the most intelligent person in the room”. Biddiss was picked to work with Scott on the long-awaited second Gladiator film after working with him on Napoleon. He was hired because of his experience at handling large numbers of supporting artists, and training film “extras” to behave like military forces from different historic eras. He spent eight months on the project. Sometimes it was necessary to work while a desert sand storm raged around ranks of new recruits who had been provided with masks and goggles to cover their faces. But Biddiss said the most difficult challenge on Gladiator II, filmed in Malta, Britain and Morocco, was reproducing a particular battle scene with the Praetorian Guard. “It was very hard to choreograph this drill because Ridley wanted the men to move together in a coordinated way that was very hard to achieve,” he said. While the adviser has often worked on location, reproducing large military encounters, his expertise also covers creating the illusion of proficient gun handling and espionage practice. “I find, as do the secret services, that females are much more surveillance aware and much more situationally aware. They need to be,” Biddiss said. “Men are generally not like that. Their initial instincts, when you train them, are more predatory, and so they miss things. As a result, women are much harder for professionals to follow.” Playing the role of a hired assassin for The Day of the Jackal, Redmayne needed to learn covert techniques and, in training, was told to follow a fictional agent called Zara, a role taken by Biddiss’s wife, Debbie. “He found it hard. It is proof that women are so much more aware and harder to track on the street,” Bidiss said. “Even with my knowledge of the techniques,” he added, “I would find it more difficult to follow a female agent.” Biddiss also trained the British actor Lashana Lynch, who starred in the latest James Bond film and plays Bianca in The Day of the Jackal. She was instructed in surveillance, lock picking, close-quarters weapons training and the kind of “dirty fighting” that was once practised by Special Operations Executive agents during the second world war. “During world war two, the women working for SOE were among the very top performing agents. There are many stories that are not widely known yet, and I would like them to come out so these women could get the credit they deserve,” Biddiss said. “And today it’s true that using a mobile phone as a weapon, which is what Eddie was talking about with Graham Norton, is a real thing. You can gain enough time to get away from an assailant like that. You can also use the screen as a mirror to watch someone who’s following you.”