Unionists point to the presence of three IRA suspects awaiting trial in Bogotá over allegations that they trained Farc guerrillas. The trio includes James Monaghan, a convicted IRA man and weapons innovator. It was Monaghan back in 1973 who invented the IRA mortar.
Alongside Monaghan is Martin McCauley, a leading figure in the IRA's engineering department who has perfected home-made mortar-like missiles. The Colombian military says McCauley's imprint has been evident in recent Farc attacks.