The president of Ireland, Michael Higgins, has been welcomed by the Queen to Windsor Castle at the start of the first state visit by an Irish head of state.

Members of the Grenadier Guards towered over Higgins as he inspected the guard of honour.

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The President of Ireland Michael D Higgins is dwarfed by troops of the Queen's Company, Grenadier Guards as he inspects the guard at honour during the first ever state visit to Britain by an Irish head of stateReuters

The visit is a symbol of how Northern Ireland's peace process has transformed relations between Britain and Ireland. Higgins, a veteran leftwing politician, poet and human rights activist, said it was impossible to "wipe the slate clean" about the past but relations between the two countries were good.

Higgins was to address both houses of parliament — another first — during his three-day trip, which includes a banquet at the castle, hosted by the Queen. Among the guests will be Martin McGuinness, once a senior IRA commander, now Northern Ireland's deputy leader.

The IRA killed nearly 1,800 people during its 27-year campaign of violence aimed at wresting Northern Ireland from Britain, among them the queen's cousin, Lord Louis Mountbatten. McGuinness was the IRA's chief of staff when the group assassinated Mountbatten in 1979.

In 2011, the Queen became the first reigning British monarch to visit the Republic of Ireland. The following year she and McGuinness shook hands in a brief but minutely choreographed meeting.

The President of Ireland prepares to inspect a guard of honour with Prince PhilipReuters
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Major Andrew Seddon, captain of the Queen's Company Grenadier Guards, invites Mr Higgins to inspect the guard of honourGetty
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The Queen smiles as she talks to Mr Higgins during the ceremonial welcome at Windsor CastleGetty
The Queen and the President of Ireland board the Australian State CoachAFP
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The coach carrying the Queen and Michael Higgins arrives at Windsor CastleAFP
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Members of the Band of the Irish Guards are reflected in a brass instrumentAFP
Members of the Household Cavalry gather for the ceremonial welcome for Irish President Michael D HigginsGetty