In the early 1970s, the British Army ran a secret undercover unit. Its existence was deniable and its tactics were so controversial that the unit was disbanded after just 14 months. Now, for the first time in 40 years, some of the unit's former members break their silence and talk candidly to John Ware about how they took the war to the IRA, sometimes even imitating the IRA itself. The soldiers believe they saved many lives. But Panorama's new evidence reveals that some members of the unit opera...