One can only wonder what thoughts went through Queen Elizabeth’s mind as she shook hands with Martin McGuiness, the deputy First Minister of Northern Ireland, in Belfast on Wednesday.

McGuiness was reputedly a commander in the Irish Republican Army (IRA) -- the same IRA that killed Lord Mountbatten, the uncle of the Queen’s husband, Prince Phillip, in August 1979.

On a two-day trip to Northern Ireland, the Queen has not only visited an Irish Catholic Church (quite historic since she is the head of the Church of England), but also met with a man (McGuiness) who had spent much of his adult life trying to overthrow British rule in Northern Ireland.

While McGuiness himself has claimed that he left the IRA in 1974 (five years before Mountbatten’s assassination), the true extent of his membership in the militant organization and what crimes he may have committed remain fiercely debated.

As for Mountbatten, it has now been more than three decades since he was blown up by an IRA bomb off the coast of Eire.

The Last Viceroy of the British Indian Empire and a military hero of the Second World War, the 79-year old Mountbatten was killed in a fishing boat near his summer home in Mullaghmore, County Sligo (in the Republic of Ireland), only 12 miles from the border with Northern Ireland.

Ignoring advice from the Garda (the national police service of the Republic of Ireland) that he might be a target for Republican terrorists, Mountbatten decided to go tuna fishing and lobster trapping. The night before, a member of the IRA named Thomas McMahon, somehow sneaked into the boat and placed a 50-pound radio-controlled bomb, which was later detonated remotely from 200 yards away.

After the blast, local fishermen tried a rescue and pulled Mountbatten’s body out of the water -- but his legs were already severed and he died shortly afterward.

The powerful explosion not only killed Mountbatten, but also his grandson, Nicholas Knatchbull, 14, a local boat boy named Paul Maxwell, 15, and the Dowager Lady Brabourne, 82, who was another passenger on the fishing boat.

Three people on the boat survived the attack, including Timothy Knatchbull, 14, – Nicholas’s twin brother – who was blinded in one eye.

Two men McMahon, then 31, and Francis McGirl, 24, were charged with Mountbattten’s murder following one of the biggest manhunts in Irish history.

The IRA boasted of the assassination, citing it was meant to “bring to the attention of the English people the continuing occupation of our country.

Gerry Adams, the head of Sinn Fein, the political wing of the IRA, once “defended” the murder of Mountbatten by claiming: What the IRA did to him is what Mountbatten had been doing all his life to other people; and with his war record I don't think he could have objected to dying in what was clearly a war situation.”

Adams added: [Mountbatten] knew the danger involved in coming to this country. In my opinion, the IRA achieved its objective: people started paying attention to what was happening in Ireland.

At the memorial service in December 1979, the Queen’s son, Prince Charles, who was quite close to Mountbatten, condemned the “subhuman extremist that blows people up when he feels like it.”

Due to a lack of sufficient evidence, McGirl was acquitted of murder charges and he later died in 1995. McMahon was convicted, sentenced to life in prison, but he was freed from prison in 1998 in connection with the “Good Friday” peace pact.

As of August 2009, McMahon was still alive and found in a bungalow in Lisanisk, near the town of Carrickmacross in County Monaghan, in Ulster, where he was working as a carpenter.

Interestingly, McMahon reportedly helped with McGuiness’ presidential campaign.

What is sometimes forgotten is that on the day of Mountbatten’s assassination, the IRA also ambushed and murdered 18 soldiers of the British Army, including sixteen at Parachute Regiment at Warrenpoint, County Down.