A SOLDIER who guards the Queen has been arrested after he was found to be an illegal immigrant. It is believed he joined the Army under a false name - and his real identity was uncovered only after a car crash. In the meantime he had been trained in marksmanship, grenade throwing, how to use a rocket launcher, and the Army's Bowman radio system. The soldier, from an African Commonwealth country, joined the elite 1st Battalion Irish Guards and even took part in the Trooping the Colour in front of the Royals last month. A senior military officer told The Sun: "This is a blunder of unparalleled proportions. For an illegal immigrant to gain membership of any Army regiment is unbelievable when you consider the potential damage an enemy could do there. "But to be accepted into a Guards regiment, and therefore to have such close proximity to the monarch, is nothing short of a scandal." Palace officials were "extremely unhappy" when told of the blunder. A source said: "There have been Royal security breaches in the past but to find out the problem came from within the Queen's personal guard is astonishing." The soldier, named only as Guardsman Kapinga, joined up in November 2008. He underwent training at Catterick, North Yorks, before joining the Irish Guards regiment this summer. He was then stationed with the 1st Battalion Guards and took part in sentry duties in the familiar red tunic and bearskin at Windsor Castle. It is understood Kapinga was living in the country using forged documents when he joined up. The fakes were not spotted by the recruiting officer, or checked again. Kapinga was arrested by Hampshire cops after an accident on Monday and was found to have numerous aliases. The Irish Guards, based in Windsor, are on a two-year tour of ceremonial duties. A source said: "This is incredibly embarrassing. Clearly the vetting procedure was not as thorough as it should have been."