A 1966 picture of Shadow V, with Lord Mountbatten in the front Copyright: Malcom Aird/Robert Estall Agency

We drove into the village, turned into the harbour and proceeded carefully along the harbour wall. ‘Shadow V’ was on the outside of ‘Celtic Dawn’, Rodney Lomax’s black fishing boat. Because the tide was low, we had to climb down a metal ladder attached vertically to the wall. This was no problem for (his twin) Nick and me but we were frightened as we helped our 83-year-old grandmother (Dowager Lady Brabourne) and 79-year-old grandfather (Lord Mountbatten) down the greasy, salty ladder. The two guards who had tailed us from the castle also helped them down and across Rodney’s boat into ours.

In Granard, Thomas McMahon and his accomplice did not say anything that betrayed their actions earlier that morning. They had climbed aboard ‘Shadow V’ and hidden five pounds of gelignite under the deck close to where we were all standing. It was probably in a plastic tube 17 inches long and about three inches wide. Gelignite, also known as dynamite, gives off a powerful smell of almonds. When Thomas McMahon prepared the explosives he would have done so in a well-ventilated place to prevent getting a blinding headache. The bomb would have been wrapped in plastic which would have reduced the smell.

Any remaining odour would have been masked by the salty, fishy air of the harbour, mixed with the fumes from ‘Shadow V’s’ cranky old diesel engine.

Nicholas (left) and Timothy with their mother Copyright: James Crathorne

My father’s account continues: ‘We left the harbour at about 11.35 am.

Dickie remained at the helm, which was the first time that he had done so this year. Usually, he allowed the children of various ages to steer the boat in and out of the harbour.’ Members of an IRA Active Service Unit now kept a careful eye on us and our two friendly Gardai (police), who went to our car, removed the keys from the ignition and locked it. Next the Gardai got into their patrol car and with Kevin Henry at the wheel drove alongside us on the coastal road.

My mother was sitting with her legs stretched out and her back resting against the stern, on the left side of the boat, with Twiga (their dachshund) on her lap, and an old copy of the New Statesman which she had not yet had time to read.

Lord Mountbatten with his grandsons — the twins Timothy and Nicholas Copyright: Trustees of the Broadland Archives

I was … hovering close to the helm in case my grandfather decided he no longer wanted to steer. Nick was close by, perhaps with the same thought in mind. When Paul (Maxwell, a local boy) asked if I had a watch on, time seemed strangely irrelevant in such perfect conditions.

I playfully examined my black plastic Casio watch and announced,‘Eleven thirty-nine and forty seconds.’ As I did so, my grandfather was using full power and we were cutting through the water at about15 or 20 miles per hour. He obviously intended on staying at the helm, so I decided to get up on the cabin roof as an extra pair of eyes…

It seemed anyone who had a boat was on the water that morning. Dick and Elizabeth Wood-Martin, in whose borrowed pram Nick and I had passed a good deal of time as infants, were out in their boat… Church of Ireland minister Canon Thomas Wood, chaplain at Sligo General Hospital, was out with his son fishing for mackerel and pollack and later recalled my grandfather waving at him.

Another of the boats we passed was a 13-foot Avon dinghy. On board were the owner Charles Pierce, a long-standing visitor to the area, his wife Kathryn, and her brother-in-law William Wilkinson. He later recalled:

We were fishing for mackerel roughly about a 100 or 150 yards off the shore when Charles said to me, ‘Did you ever see Lord Mountbatten before?’ ‘Well,’ I says, ‘I have seen him on the television and read about him.’ ‘So,’ he says, ‘there he is just coming out from the harbour.’ So, of course, I was very interested to see Lord Mountbatten in the flesh. As the boat came along I could see him standing up. I could see his white wavy hair coming along and I noticed other people in the boat.

On the cliff top about 200 yards away, the Gardai had parked close to a caravan opposite our lobster pots… as my grandfather slowed the boat, my grandmother turned to my mother and said, ‘Isn’t this a beautiful day?’

William Wilkinson again:

As the boat approached us I had lost a wee bit of interest in the fishing as I wanted to focus my eyes on this man, for nosiness shall we say, because I had never seen him before. As the boat got closer I was given a nice clear view of him because he wasn’t much further than maybe about 30 yards. The boat passed and I said, ‘This boat is moving towards the shore or rocks.’ Charles replied, ‘He is probably going over to lift lobster pots.’ When it was about 60 yards away, I still had it under observation when all of a sudden there was just this ‘boom’.

According to Garda Mullins, at 11.46, ‘Suddenly I heard an enormous bang. I saw the boat go up in pieces in the air. There was a lot of smoke and in a second the boat had disappeared. All I could see were very small pieces of wood floating on the water.’

My father later wrote:

My first memory is of a crack, rather than a bang, and then I regained consciousness under the water, being swirled round and round and head over heels. I did not stop to wonder what had happened. I just knew an absolute disaster had occurred…

My mother wrote in her diary:

I only remember a terrific explosion (and thinking it was the engine which had been playing up) and immediately being submerged and going down and down in the sea with water rushing in ears. Frightened I would not get up before drowning (forgot it was shallow) or get caught beneath hull. Remembered Darling Daddy’s story of Kelly sinking. Put my hands over nose and mouth to stop swallowing water and made a note to tell him I had if I got up. Remembered Dodo could swim but worried she would get bad chill. It finally got lighter and I surfaced hitting a piece of wood and not minding facial injuries I later thought caused by it! Mentally relieved to hear Darling John’s agonised voice shouting ‘Help my wife’ or ‘Where’s my wife’ quite close. Vaguely aware of other voices before mercifully losing consciousness.

My grandfather was at the helm three or four feet behind me and slightly to my right. The gelignite under the deck must have been between us because as we rose into the air we went in different directions. I remember a sensation, as if I had been hit with a club, and a tearing sound. I do not remember my journey through the air or hitting the water but before the debris finished raining down, I was unconscious and about 100 feet from my grandfather.

Eighty-six miles away in Granard, the Gardai had no idea what had just happened outside Mullaghmore but they were convinced they had stopped two IRA men involved in a serious crime and they now decided to act.Within five minutes of the explosion Garda James Lohan stepped up to Thomas McMahon and said, ‘I am arresting you under section 20 of the Offences against the State Act 1939. You are not obliged to say anything unless you wish to do so but anything you say will be taken down in writing and may be given in evidence.’ McMahon made no reaction. Next Lohan went to the man who had been driving him. The Gardai were soon to find out that his real name was Francis McGirl. As Lohan used the same words, his right hand on the prisoner’s shoulder, McGirl sat and grinned.