England's Queen Elizabeth made her first trip to Ireland Tuesday, but not before a bomb squad was called to diffuse an explosive device before her arrival.

Irish army experts were called after what was thought to be a pipe bomb was discovered on a Dublin bound bus outside the city.

"This one was probably designed to disrupt the Queen's visit (but) not necessarily to go off," said Conservative MP Patrick Mercer. "A pipe bomb goes off on impact unless it has a sophisticated timer which is unusual."

The Queen's four day trip was designed to foster a developing peace between Great Britain and Northern Ireland. Relations between the two have remained strained.

"This is the start of an entirely new beginning for Ireland and Britain," said Irish Prime Minister Enda Kenny. "I really do hope that the welcome she gets will be genuine and memorable for her.

Britain and Ireland have a long history of bloodshed in Ireland's struggle for independence. Tuesday's visit was the first by an English monarch since the Republic of Ireland was founded in 1922.

More than 8,000 police are on duty during the queen's stay -- the tightest security ever seen in the country.