Flagstaff hill incident The Flagstaff hill incident was an international incident between the Republic of Ireland and the United Kingdom which took place on the night of 5 / 6 May 1976 near Cornamucklagh , County Louth , Republic of Ireland , when the Irish Army and Garda Síochána arrested eight British Special Air Service soldiers that had illegally crossed the border . Background . The worsening security situation in south County Armagh , especially after the killing of three British soldiers at an observation post in November 1975 and the massacre of ten Protestant workers in January 1976 , prompted British PM Harold Wilson to send in hundreds of members from D squadron of the Special Air Service , who were deployed to Bessbrook Mill . The ambush of the observation post exposed the fact that conventional military skills hadn ' t worked in South Armagh , since the Army report of this incident identifies a number of basic mistakes regarding camouflage , routine patterns and the observation post ' s arrangement . On 28 October 1971 , a major confrontation took place between British and Irish troops at a cross - border bridge between the Republic and Northern Ireland , at the village of Munnelly , between counties Fermanagh and Monaghan . A British patrol were laying explosive charges to destroy the bridge , as part of an effort to destroy bridges and roads being used by the IRA to import arms and supplies . A Garda Síochána officer stated that the bridge was at least half in the Republic , and the British commanding officer disputed this . The Irish Army then deployed a unit of soldiers armed with submachine guns , and the Irish commander demanded that the British surrender their explosives . Following a 90 - minute standoff , the British withdrew . The first high - profile action carried out by the SAS in 1976 was in March when it captured Sean McKenna , an IRA volunteer wanted for attempted murder and a string of other offences . He was caught at 2 : 30 am while sleeping at home in Edentober , on the Republic ' s side of the border , in a cross - border raid by the SAS . In April , the SAS killed IRA member Peter Cleary in controversial circumstances near Forkhill , just 60 yards inside Northern Ireland . Although the porous nature of the border had led to 189 inadvertent border - crossings by the British security forces in the past two years , these latest incursions put the Garda Síochána on alert . Another worry for the Irish government was the activity of loyalist squads in the area , which had kidnapped and killed a man near Dundalk four days before . The incident . After the murder of Seamus Ludlow , the man kidnapped and shot near Dundalk , Irish military and police forces stepped up their presence along the border . A checkpoint was set up by members of the Gardaí and the Irish Army on Flagstaff Road in the townland of Cornamucklagh , some 700 yards inside the Republic . At 10 : 40 pm , the Gardaí stopped a Triumph 2000 car coming from the north with two men inside . The driver obeyed the signal to stop , but when questioned by the policemen about their destination , they avoided a straight answer . They were asked to step out of the vehicle , after one Garda noticed that the passenger had what seemed to be a gun hidden under a map . The unidentified men were unwilling to leave the car until Irish Army soldiers came out of the bushes and pointed rifles at them in support of the Gardaí . The two men , who wore plain clothes , were Fijian - born trooper Ilisoni Ligari and trooper John Lawson , both members of the SAS . After searching the car , the policemen found a sub machine - gun and a Browning pistol . The Gardaí immediately arrested them , with the help of the Army , and took them to nearby Omeath Garda station . Lawson initially claimed that they were off - duty soldiers who became stranded while test - driving the car , and Ligari refused to talk about " the mission we were on " . It later transpired that Lawson and Ligari were in the area to collect or relieve Staff Sergeant Malcom Rees and Corporal Ronald Nicholson ; two SAS members carrying - out surveillance from a hidden observation post on Flagstaff Hill , which is just inside Northern Ireland and overlooks Carlingford Lough . According to author Peter Taylor , Rees and Nicholson were actually deployed on the Republic ' s side of the border . When the soldiers manning the surveillance post failed to meet Ligari and Lawson , they radioed Bessbrook Mill . They initially suspected an IRA ambush . Four plain - clothes SAS soldiers – troopers Nial McClean , Vincent Thompson , Nigel Burchell and Carsten Rhodes – were sent to search for their missing comrades in two cars , picking - up the two men from the observation post in the process . The team was carrying another three sub machine - guns , a pump - action shotgun and 222 rounds of ammunition . The first vehicle – a Hillman Avenger carrying Thompson , McClean , Rees and Nicholson – came upon the Garda checkpoint at 2 : 05 am . Rees and Nicholson were still wearing British Army uniforms . The second car – a Vauxhall Victor with Burchell and Rhodes – was stopped shortly after . Sergeant Rees tried to explain the situation to the Gardaí : " Let us go back . If the roles were reversed we would let you go back . We are all doing the one bloody job " , but he eventually ordered his men to lay down their weapons when Irish Army soldiers surrounded both cars and aimed rifles at them . The Gardaí unit , commanded by Sergeant Pat McLoughlin , called for instructions on how to deal with the men now in custody . The shotgun drew the attention of the Gardaí since the same type of weapon was used in three recent murders in the area . Omeath Garda station was ordered to keep the men in custody until a decision was taken at a political level . Before dawn , it was decided that the SAS team be transferred to Dundalk Garda station . Diplomatic consequences . The detention of eight SAS men put Irish Taoiseach Liam Cosgrave and his coalition government in a dilemma ; if he had the soldiers released without charge , he was giving a green light for further British incursions into the Republic , but if he let them go on trial and they were convicted , diplomatic relations with Britain would be at risk . A report published by Mr Justice Henry Barron in 2006 revealed that the soldiers were questioned about the three murders , especially that of Seamus Ludlow . The SAS men were also questioned about the 1974 Dublin and Monaghan bombings , and the weapons were checked in relation with the murders . Both protesters and media camped outside Dundalk station . There were concerns that the station could be attacked at any moment . The detainees were eventually moved under heavy armed escort to Dublin , where they were charged by the Special Criminal Court with possession of firearms with intent to endanger life and for carrying firearms without a certificate . The charges carried a maximum sentence of 20 years in prison . The soldiers were released on bail after the British embassy paid £40 , 000 . A helicopter flew them out of the state . The British Army Minister , Bob Brown , apologised to the Irish government but dubbed the incursion " a mistake " . The British government , embarrassed by the situation gave top priority to the immediate release of the soldiers . Arthur Galsworthy , then British ambassador to the Republic of Ireland , stressed his worries about the finding of a shotgun and a dagger among the weapons confiscated by the Gardaí . Another concern was that most of the soldiers were in plain clothes , and that the two groups told different accounts of their presence in the state . When it became clear that a trial was unavoidable , the British government hardened its position , with a member of the Foreign Office proposing economic sanctions against the Republic and even the creation of a " buffer zone " along the border , which would have created " a no - man ' s land in which the terrorist could do what they would " . A confidential memo from the Northern Ireland Office also called for pressure on the Irish government to discharge the soldiers on the grounds that the safety of the SAS men in prison couldn ' t be guaranteed . Aftermath . The eight SAS men stood trial in March 1977 . They were each found guilty and fined £100 for possession of arms and ammunition without firearms licensing . The weapons were returned to the British Army after forensics established that they were not used in any crime inside the Republic . A British military source later explained that the use of a 1 : 63 , 000 scale map instead of the 1 : 20 , 000 led the SAS men south of the border . During 1976 , there were another 54 incursions by British forces inside the Republic ' s boundaries . On 28 October 1986 there was another cross - border incident in which a British soldier was arrested by the Gardaí after an IRA mortar attack on Drummuckavall British Army watchtower in County Armagh . A red Ford Escort was pursued while escaping across the border towards Thomas Murphy ' s farm by soldiers of the Scots Guards . One of the Guards , a Lance Corporal , broke into a shed , where he was confronted by two IRA members . The guard had inadvertently crossed the border and after a brief brawl with the two men , a Gardaí patrol arrived at the scene and arrested the soldier for possessing an illegal firearm . He was taken to the Gardaí station at Dundalk , but was released six hours later after negotiations between senior RUC and Garda officers .