article: However, much of the attention will fall on Sinn Féin's Martin McGuinness, who recently tried and failed to win the role currently held by Mr Higgins. Mr McGuinness, a former IRA man and life-long republican, will be among the monarch's guests at Windsor Castle. He met the Queen in 2012, but the visit still holds challenges for Sinn Féin. The UK state visit marks another significant milestone in Anglo-Irish relations and further fascination for those who have followed Mr McGuinness' long journey from paramilitary to politician to palace guest. BBC News looks back at the significant events and political choreography affecting Sinn Féin's relationship with royalty. The government deploys the Army to Northern Ireland following widespread civil unrest and violent sectarian clashes between Catholics and Protestants. The deployment, known as Operation Banner, was to become the longest continuous campaign in the Army's history. Martin McGuinness, aged about 20, joins the Irish Republican Army (IRA) and quickly becomes an influential figure within the paramilitary organisation in his native Derry. Interviewed by the BBC during a walkabout in the city, a baby-faced McGuinness does not correct the correspondent when he described him as the "Officer Commanding for the Derry part of the IRA Provisional operation". Martin McGuinness is sentenced to six months in prison by the Republic of Ireland's Special Criminal Court, after he was caught in a car containing large quantities of explosives and ammunition. He tells the court he is "very proud" of his IRA membership. The Queen's cousin, Lord Louis Mountbatten, is killed by an IRA bomb while on holiday in County Sligo in the Republic of Ireland. Two of his relations and a 15-year old local boy are also killed in the explosion. Hours later, 18 soldiers are killed in a double IRA bombing at Warrenpoint, County Down. It is the highest death toll suffered by the Army in a single incident in Northern Ireland. Martin McGuinness is elected to the British House of Commons as a MP for Mid Ulster. Adhering to Sinn Féin's long-standing policy of abstentionism, he refuses to take his seat or swear an oath of allegiance to the Queen. The Good Friday Agreement is signed in Belfast following years of intensive peace talks between political parties in Northern Ireland and the British and Irish governments. Martin McGuiness was Sinn Féin's chief negotiator during the deliberations. The accord paves the way for devolution through a new power-sharing coalition of unionists and nationalists at Stormont. Martin McGuinness, who left school at the age of 15 without any formal qualifications, is appointed as education minister at the Northern Ireland Assembly. The IRA releases a statement saying it has "formally ordered an end to the armed campaign". The paramilitary organisation, believed to be responsible for more than 1,700 deaths over a 35-year period, says it it now committed to "exclusively peaceful means". Martin McGuinness becomes deputy first minister of Northern Ireland after an election that followed a power-sharing agreement between Sinn Féin and the Democratic Unionist Party. He forms an unlikely political relationship with his former foe Ian Paisley,
summary: The Queen is hosting the first ever UK state visit by an Irish president, as Michael D Higgins begins a four-day diplomatic mission to Great Britain.