GRANDAD was a wonderful storyteller. He was always telling quirky tales, like the time he went fishing using depth charges (underwater explosives). Or he would talk about his own grandfather, who bred whippets and believed the best way to shorten their tails was to bite them off. Really, though, as a youngster I wanted Grandad to tell me about "goodies" and "baddies" and whether or not he had personally killed anyone in his navy days during the second world war; such was my cartoon understanding of warfare at the time.

My grandad died this month. For 18 long months, his body - which had given him a distinguished career - had held him as an undignified prisoner, following a paralysing stroke. As the family pulled together to compile a eulogy, his stories were gathered. Seeing them as a collection had a profound effect on me. They were amazing and inspiring in equal measure.

But they have also become an uneasy mirror to hold against my own life. The comparison made me feel inferior, cowardly even. It forced me to question what kind of person I am, what kind of society I live in, and how times have changed since my grandfather, Jim Melville, was born into a mining family in the village of Fence Houses, south of Newcastle, on October 5, 1923.

Even before he was born, war was shaping Jim's life: his father, also James, was gassed during the first world war at the battle of Ypres. Fortunately he survived and returned to Britain where he had two children with his wife, Annie. Sadly, Annie died when Jim was only seven, leaving his sister, Dorothy, to take on the role of housekeeper and carer. Two years later, James senior remarried and Dorothy left home. The relationship between Jim, his father and step-family soon deteriorated. Then, with war declared across Europe, Jim lied about his age to enlist in the navy. He was 15 years old.

When I think about how I was at 15 - lying about my age merely to get my hands on alcohol - I cannot help but be in awe of his bravery. "Son, there was a war on - that really didn't matter," was his typically curt reply when I once asked him why he signed up so young. As with the majority of his amazing life, he was quick to play down the significance of his deeds.

The big differences between his world and mine, 60 years apart, are obvious. But for me, it is the little details that are the most remarkable. I first tried smoking outside the local chip shop; Jim Melville had his first cigarette on board the battle cruiser HMS London.

Somewhere in the North Sea, Jim's ship encountered heavy fog and he was sent to the crow's nest to try to see above the gloom. The air was freezing, the ship rocking and he had no safety harness. He later told me it was one of the most terrifying things he ever had to do. If there were any enemy planes patrolling nearby, his head was the only thing sticking out above the clouds. When he finally got back to the deck to report that there was nothing more to be seen from the top of the mast, a ranking officer handed him a smoke, saying: "Here you are, Melville; this should calm you down."

As Able Seaman Melville, Jim continued to serve on HMS London among many of the notorious Russian convoys: huge processions of freighters and their escorts taking provisions to the beleaguered Soviets while under continual attack from the German Luftwaffe and U-boats. When this wasn't happening, most of his time was spent chipping ice from the ship's superstructure to stop her capsizing.

My first job was also as a crew member - in the Ayr branch of McDonald's. On busy days, I felt like I was under continual attack from unreasonable managers and pernickety customers. When this wasn't happening, most of my time was spent trying to do as little as possible and occasionally sneaking a chicken nugget from the kitchen.

After leaving school, I travelled to America to spend a year living as a high school senior. I arrived in Wisconsin on September 3, 2001 and a little over a week later, I felt I had made a big mistake. Watching the endless streaming of news on 9/11 (there were some cable channels commandeered to bring incessant terror updates) and hearing wild, fanciful, yet still unnerving speculation about what might happen next (a chemical attack on all the major malls; the hijacking of boats on the Great Lakes), is probably as close as I have been to actual conflict. I certainly felt no urge to sign up to fight when, a couple of years later, amid global protests and dubious motives, coalition forces declared war on Iraq.

The war my Grandad took part in was different, at least on the face of things: he fought with the full support of his country in a battle for survival. But listening to him made me realise that the second world war was no less ugly than the conflicts of today. As I got older, Grandad began to tell darker stories detailing the atrocities he had witnessed. Recounting them frequently reduced him to tears. Yet, his natural ability to spin a yarn created a vivid image of people left with little other than hope.

He endured kamikaze attacks from Japanese pilots whose faces he could see before they plunged to their deaths, and watched a Japanese submarine sink an Allied supply vessel. In response to the latter, his British destroyer torpedoed the assailants. After watching people dying on board the stricken supply vessel (including a woman who became lodged in a porthole and slowly drowned), Jim, along with a sailor known as Lofty, was sent out into the darkness in a rescue dinghy to find survivors.

After several people had been hauled on board, a Japanese sailor pulled himself onto the side of the boat, presumably for rescue. Lofty put a gun against the man's head, only for Jim to order him not to shoot - insisting he should be taken prisoner. What neither Jim nor Lofty knew was that this was another kamikaze attack - a suicide bomber, who had just pulled a pin from a grenade on his jacket.

The blast tore a hole into the side of the dinghy, costing Lofty his legs below the knees. As it began to sink, with Jim, his wounded comrade and a number of terrified civilians on board, Jim believed all was lost. Yet, as the water rose, in the distance, he heard a lone piper playing from the deck of his destroyer. Salvation had come.

All of this happened before my grandad was 23. At that age, my chief concerns were utterly trivial in comparison; how to avoid another class at university, how to extend my overdraft, and so on.

The end of the war brought Jim happiness when he was introduced to Win, a sister of his best friend Ted. Win was the woman he would marry and start a family with. However, the end of the war did not bring the end of service. One of Jim's first post-war postings was to Palestine in 1946 to help prepare for the foundation of Israel, where he served under the famous Lionel "Buster" Crabb, a daring frogman whose 1956 disappearance is still the subject of conspiracy theories.

Crabb's specialist unit wore plain clothes without any insignia and were known locally as Buster's Light Horse Brigade. Many of the exact details of their operations remain classified, though it seems that mine-removal and counter-terrorism formed part of their duties. One of Jim's service reports from this time said that he had "plenty of flannel, but the initiative to carry it out". Coincidentally, I also spent time in Israel, aged 24, though my days were spent lounging in the sunshine and eating too much. I doubt any report on me would have read so favourably.

Learning about my grandad's extraordinary life has been a fascinating experience. Would I be able to face the prospect of world war as he did? It seems unlikely I will ever have to find out. As my grandad once said, on the verge of tears after one of his sadder stories: "If it does happen, it'll never be like that again, son. Thank God."

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