Updated: 15:20 EDT, 23 May 2011>
It's designed to protect the President from terror attacks but Barack Obama was left red-faced after one of his armour-plated Cadillacs was brought to a halt as it left the U.S. Embassy in Dublin.
The gigantic bomb-proof General Motors vehicle, with eight-inch thick steel on its door, didn't even make it as far as the road outside the consulate.
The car had to be abandoned after the collision in front of waving crowds while Mr Obama and his wife were en route to his ancestral home in County Offaly.
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Embarrassing: One of Barack Obama's fleet of armoured cars gets stuck on the ramp of the exit of the U.S embassy in Ballsbridge Co.Dublin
Luckily, the vehicle that broke down was the spare limo used by the President's Secret Service protection team.
Mechanics rushed in to rescue the vehicle which was lodged helplessly on the ramp, while onlookers stood and watched - some of whom took video footage and photos.
The cars, worth over $1million, is 18ft in length, weighs 8 tons and 8in thick armour plating on its doors.
When the President is riding in one, the vehicle is officially known as Cadillac One. However, it's more apt nickname is 'The Beast'.
Specially built for Mr Obama, the General Motors GM.N vehiclse boasts its own oxygen supply in case of chemical attack and puncture resistant, run-flat tyres reinforced with kevlar.
However none of this, it appears, could overcome the might of a lowly speed hump.
Secret Service spokesman Robert Novy said: 'A Secret Service spare limousine, carrying staff and support personnel only, bottomed out at the top of the driveway rendering the vehicle inoperable.
'Occupants were relocated into other vehicles and the motorcade departed out another exit without further incident. There were no injuries.
'The size of our vehicles is always an issue and taken into consideration during the advance process. However, it only takes a slight miscalculation for problem like this to occur.'
The incident will bring Obama's security into question. His aides have gone to great lengths to ensure the President's safety while he's visiting the UK.
Such is the emphasis on security that Mr Obama’s team has even asked to fit bomb-proof double glazing to the windows of his guest suite at Buckingham Palace.
Stuck: The 'terror-proof' Cadillac fails to even make it on to the road outside the U.S. Embassy in Dublin
The moves to increase the First Couple’s safety come in the wake of the killing of Osama Bin Laden three weeks ago.
Also joining the President on the trip will be one military officer carrying a suitcase containing America’s nuclear missile launch codes, plus representatives of six departments of state.
Mr Obama himself will fly on Air Force One, which doubles as a flying luxury hotel and command post complete with an operating theatre and gym.
The customised Boeing 747-200B, which is accompanied by a decoy aircraft, is said to cost around £110,000 an hour to run.
After dumping The Beast Barack and his wife finally made their way to in County Offaly, the small Irish village where his great-great-great grandfather once lived and worked as a shoemaker.
He walked the thronged Main Street of Moneygall, where his thrice-removed grandfather on his Kansas-born mother's side, Falmouth Kearney, lived until leaving for the United States in 1850 at the height of Ireland's Great Famine.
Visit: President Barack Obama and first lady Michelle Obama pose with Taoiseach Enda Kenny and his wife Fionnuala at Farmleigh House in Dublin
Obama's roots in the town were discovered during the 2008 presidential campaign.
Along with first lady Michelle Obama, the president even got to hug a distant relative: Henry Healy, a 26-year-old accountant for a plumbing firm who discovered four years ago he was one of Obama's closest Irish relatives.
The first couple spent extended time greeting the people who had withstood soaking rain earlier to see them. The thrilled villagers, who had been preparing for the moment for weeks, responded rapturously, waving American and Irish flags.
Obama and his wife even had a sip of Guinness each.
Tomorrow they will fly to London, where they'll visit the Queen at Buckingham Palace and no doubt be hoping to avoid further mishaps. Again, security preparations have been underway for months.
The President’s security team have raised eyebrows at Buckingham Palace after they insisted on bringing their own bottled water.
White House staff told the Queen’s household that they could not risk Mr Obama touching a drop of London tap water – or even the palace’s own bottled mineral water.
According to sources, when one staff member asked why, they were told that ‘they didn’t want to risk a change in water in case it gave Mr President a stomach upset’.
The President and his wife are due to arrive at Buckingham Palace tomorrow morning after landing at Stanstead Airport where they will be greeted by the Prince of Wales and the Duchess of Cornwall.
The couple will lunch with the Queen before a glittering state banquet in the evening.
The Mail revealed yesterday that White House staff have brought along their own portable double-glazing style glass to cover up the 1820s glazed windows in his bedroom in case of a mortar attack
Staff have also revealed that they have been barred from using their mobile phones while the president is in residence due to the communication hardware his security team have brought with them.
And all servants have been subject to a criminal record check, even if one has been carried out already.