Like most people who don't know Mann personally, I first spotted him in Paul Greengrass's film Bloody Sunday, and I wrote at the time, "Greengrass's smartest piece of casting is Simon Mann, a chiselled SAS veteran of several tours in Derry, who makes an authentically no-nonsense fist of playing Colonel Derek Wilford, commanding officer of One Para. Wilford instructs his Paras to ‘scoop up’ selected ‘yobbos’ on the march, and fire if fired upon (‘Plenty of rounds!’)."
Mann's best line in the movie, though, comes in the wake of the terrible slaughter to which Wilford has exhorted his men: ‘We’ve just fired a fucking horrendous amount of ammunition, we’ve got to know why, and we’ve got to have some weapons...’ I think I know better now why Mann was so convincing here. (Paul Greengrass, interestingly, has been quoted describing Mann as "very English, a romantic, tremendously good company". Yes, I would imagine.)