Classiebawn Castle, Co Sligo

Along the windswept coast from Sligo towards Bundoran, a grey stone building, standing remote and solitary, dominates the landscape near the cliff edge at Mullaghmore Head. Shadowed by Benbulben and overlooking Donegal Bay, Classiebawn castle, with its turrets and battlements, looms up like the setting from a Gothic novel. Far below, Atlantic waves batter the rocks. Mists can roll in here quickly, leaving the castle barely visible, and seeming to float in the air. Even without knowing of the events which took place 30 years ago, this is an atmospheric, eerie place. On a pillar at the gate lodge are inscribed the initials of the castle's most distinguished former resident – M of B. They are encircled by the French motto honi soit qui mal y pense, usually translated as 'evil be to him who evil thinks'.

These days, when anyone thinks of Mullaghmore, it's as a big-wave location on the global surf map, and not as somewhere with negative associations with the past, according to well-known Bundoran-based surfer Richie Fitzgerald.

"Surfing is the main tourist attraction here. The village boasts a great sailing club too, and it would also be well regarded as an unspoilt holiday location for families," he says. "The beach is especially sheltered. There's very little swell until a quarter of a mile along the bay when the coast opens up to the full force of the north Atlantic." Last week, August holidaymakers were centered around the Victorian stone harbour that is the main hub of the village. Fishing boats were tied along the harbour wall near neat stacks of lobster pots, contrasting with cabin cruisers and yachts moored in the shallow water. Larger pleasure boats bobbed out in the bay, the still water only broken now and then by a waterskier or kids in wet suits larking about in dingies. Smaller children played nearer the shore, rockpooling with small fishing nets or building sandcastles. Most likely, it was much like the scene at Mullaghmore harbour on the morning of 27 August l979.

Peter McHugh's family have run the Pier Head Hotel, right on the harbour at Mullaghmore, for generations. "My most vivid memory is how beautiful that morning was. A bit like this year, the summer of 1979 had poor weather. But that Monday dawned with the promise of an idyllic day ahead. There was an almost peculiar stillness throughout the village and along the water. Most people were up early to take advantage of the fine weather."

Among those was the most titled victim of the Northern Ireland conflict – the queen of England's cousin, great uncle and godfather to Prince Charles, supreme allied commander in southeast Asia during the second world war, the last viceroy of India, 79-year-old Lord Louis Mountbatten of Burma. To many villagers by that stage, Mountbatten was just the elderly retired gent who loved to holiday in Mullaghmore every summer with his family and grandchildren. The family would arrive by ferry to Dublin and decamp northwest to Classiebawn castle, usually for the entire month of August.

The castle was built in the 1840s by Lord Palmerston, who served two terms as prime minister of Britain. He also built the circular stone harbour. But Palmerston's best-known Irish legacy is his less-than-humanitarian behaviour during the famine. Over a thousand tenants on Palmerston's vast Sligo estates were evicted by his agents and forced to emigrate to Canada. The building of Classiebawn was completed by the mid 1870s and succession passed to the Ashley family. It was through his marriage to Edwina Ashley in 1922 that Louis Mountbatten was to eventually benefit with sailing and holidaying in Mullaghmore.

"He'd been coming here for around 25 years, arriving with the whole Mountbatten entourage every August," says McHugh. "The village would all look forward to it as it brought a lot of colour and excitement for a few days. But after that, it would wear off and everybody just got on with things. He liked to keep a pretty low profile, swimming with the grandchildren, fishing for shrimps, or out on the boat." A regular companion on the sailing trips was 15-year-old Paul Maxwell from Enniskillen who had landed a summer job as 'boat boy' on Mountbatten's distinctive green vessel, the Shadow V.

With fine weather looking set for the day, Mountbatten left Classiebawn in his White Ford Granada on the morning of 27 August to make the two-mile drive to the harbour. Some other family members remained at the castle. His sailing companions on the day were his daughter Patricia Brabourne and her husband John, the 82-year-old Dowager Lady Brabourne, his two grandchildren, 14-year-old twins Nicholas and Timothy Knatchbull, and Paul Maxwell. Watching the party set off was the police escort for the day, Garda Kevin Henry. Paul Maxwell was already at the harbour, readying the boat for a trip out to inspect lobster pots. By 11.30, all were on board and the Shadow V sailed out of the harbour. Fifteen minutes later, only a couple of hundred yards out into the bay, the boat exploded.

"I had gone out waterskiing earlier and was standing just in front of the hotel when the stillness was rocked by this huge explosion," recalls Peter McHugh. "At first, I thought it might be a gas cylinder behind the hotel or something. But within seconds Garda Kevin Henry came speeding towards the hotel. He had seen Mountbatten's boat explode just beyond the headland." A 50lb gelignite bomb, hidden under the engine during the night, was detonated by someone watching on the shore.

According to another garda, Eddie MacHale, in reports at the time, Paul Maxwell had been standing right over the engine. Mountbatten is believed to have drowned after being blown into the water. The third casualty that day was Nicholas Knatchbull. His brother Timothy lay floating in the water, unconscious, deafened, with scorched eyes, and lungs filling with blood. His mother Patricia later recalled the split second after the blast. At first, she thought the boat's diesel engine had exploded. She saw "a ball of light, the size of a tennis ball, radiating out from under my father's feet". Momentarily stunned, she came round under the water. "I was going round and round, floating among bits of wood which I had no idea were the ? boat. I was fearful of coming up under the upturned boat, but there was no boat to be trapped under. I was aware there must be a lot of injuries to my face, and I was going in and out of consciousness."

Back on the shore, Peter McHugh scrambled into a boat with a friend. "I was probably in total shock, even though I didn't see the actual explosion. There was nothing left of the boat, just bits of wood debris floating on the surface. Because there were already a few other pleasure boats out in the bay, people had begun trying to lift survivors on board. We helped as best we could. It was a surreal scene." He returned to the harbour and waited for the other boats to return. The dead and injured were laid out in front of the hotel before the ambulances arrived. People helped as best they could, including Peter's wife, who was a nurse, and paramedics staying in the village. "It was mayhem. We fashioned stretchers of sort out of old doors, or anything to hand. Nothing really prepares you for a scene such as that. I can remember the Dowager Brabourne was quite distressed and crying out." Lady Brabourne died in Sligo general hospital the following day. Patrica Brabourne came round in intensive care, her son Timothy alongside her. She was told her other son hadn't survived. "It was overwhelming. I tried to cry but could not even do that since the pain of the stitches round my eyes prevented me," she recalled. "I felt desperate – as if a part of myself had died with my son." Timothy Knatchbull has written a personal account of the day that changed his life. From A Clear Blue Sky is due for publication at the end of the month. Now a US-based management consultant and documentary film-maker, 44-year-old Knatchbull's most obvious scar from that day is that he remains blind in one eye. According to the book, the emotional scarring was greatly healed when he began visiting a bereavement counsellor in his early 30s. He no longer regularly hears the sound of explosions ringing in his ears. He has described writing the book as "challenging, difficult, rewarding, painful, but positive. The most important message is that I have no bitterness, none whatsoever. It has allowed me to grow and to lead a happy and fulfilled life." When Knatchbull married in 1998, the couple honeymooned in Ireland.

Thirty-one-year-old IRA man Thomas McMahon from south Armagh served 19 years for planting the bomb on the boat. The year before he was released under the Good Friday Agreement in 1998, his wife Rose, later a Sinn Féin councillor and mayor of Carrickmacross, said, "Tommy never speaks of Mountbatten, only the boys who died. He does have genuine remorse." His alleged accomplice Francis McGirl – who died in a tractor accident in 1995 – was acquitted. Reports at the time spoke of a third accomplice, never caught, believed to have detonated the bomb. The killing of Mountbatten was followed hours later by two IRA bombs at Warrenpoint which killed 18 member of the British Parachute Regiment.

That day, 27 August, was regarded by the IRA as a military and propaganda success. There was the suggestion that the killings on Bloody Sunday had been avenged and soon after a slogan was scrawled on the wall opposite Sinn Féin's Belfast office: "Thirteen gone and not forgotten, we got eighteen and Mountbatten." Just a few weeks afterwards, Pope John Paul II's historic visit to Ireland was confined to the Republic over fears for his safety if he travelled to Armagh. The killings were to further harden British attitudes, particularly those of the newly elected prime minister. In the following year, Margaret Thatcher ruled out any negotiations with the hunger strikers.

However, history judges the events at Mullaghmore and whether or not the queen's cousin was a legitimate target, the deaths of young boys on the boat weigh heavily in the Sligo village. "I would have known Paul Maxwell very well," recalls Peter McHugh. "He was a likeable, lively teenager, and I would see him during his holidays here, pottering around the harbour like all of us did. He was a native, from just 40 minutes' drive away, and people found it very hard to take that he was taken like that. The one thing to hold on to was that there was never any doubt that people from Mullaghmore had any hand, act or part in the killings."

The events had a profound effect on McHugh personally, and others who witnessed it. It took a long time to accept what happened and move on.

"Mullaghmore was definitely under a cloud and there were tough years afterwards. It had been a popular holiday resort for people of all persuasions as we say. People used to come regularly from Belfast, from England. After l979, some people left, never to return. But Mullaghmore has recovered. Now, the kids of former holidaymakers come here. It is still a beautiful place." Other things remain unchanged too. Paul Maxwell's father John still has a holiday home in the village. The imposing Classiebawn is now owned by the businessman Hugh Tunney, but locals still refer to it as "Mountbatten's castle". Last week, there were English accents, and German, mingling among those of holidaymakers closer to home.

And a new generation brings a different perspective. "Lord Mountbatten was murdered when I was just a four-year-old child, but the impression I've learned over the years is that he was well liked and respected in the village, and very involved with local people and events," says Richie Fitzgerald. "For some people, his being a war hero made him all the more interesting. His killing, and the fact that two children were murdered on the boat as well, left people very shocked and ashamed that something terrible like that had happened in the village. But Mullaghmore residents just want to forget the horror of what happened in 1979. As a keen sailor himself, and someone who loved the ocean and the northwest area, I'd imagine Lord Mountbatten would rather be associated with Mullaghmore's reputation as a world centre for surf enthusiasts, rather than for the way he died."