This April was the 25th anniversary of the end of the Vietnam conflict - not even officially a war - which claimed the lives of 58,000 American troops and over 2.5 million Vietnamese citizens. Fighting alongside the Americans were the hardened, jungle-trained troops of Australia and New Zealand. They were highly respected by their enemies, the North Vietnamese regulars and guerrillas ("Vietcong"), who were struggling with the American-supported South Vietnamese government for control of the country.

The conflict for many of us may now be consigned to Hollywood movies. But for Ray and his mates - British nationals who were living in Australia and were drafted into the armed forces - it is still very real.

"I can remember the sunsets," he says. "The most beautiful sunsets you've ever seen. A brilliant blue, with banana palms all around us and this fine red dust that stained all your clothes in the dry season."

He vividly remembers the nights, too: "One minute it was daylight - then it was dark. The nights could be very still. There would be this eerie silence and you would sit there thinking, 'what's going to happen?' You wanted something to happen, to break this awful silence."

Speaking quietly, he adds: "I still have nightmares today that I'm back in that jungle. If I'm silly enough to put myself in a situation where I'm walking in a heavily wooded area and it rains, sorry pal, I'm back in the jungle."

These nightmares and the legacy of the conflict on Ray, a gunner and forward observer with the Royal Australian Artillery, were to cost him his marriage and very nearly wreck his life.

He doesn't really remember the London of his youth any more, after his family emigrated for a new and better life in Australia when he was just 13. "I suppose we were sort of middle class," he says, adding that his dad was a toolmaker and his mother a housewife. "It was a happy home, a happy life and a pleasant childhood."

The Agombars moved to the small town of Geelong, about 50 miles south-west of Melbourne, home to many other European emigres. Working as an apprentice mechanic for a Ford dealer, Ray jokes that the port town was known among his contemporaries as "Sleepy Hollow". A quiet young man, he kept to himself, preferring to listen to jazz than hang out with the young farmers in the town's many pubs.

When the call up to Vietnam came, he cursed his luck. "I didn't want to fight. I wasn't a fighting man. But you didn't want to bring shame on you or your family. So you went."

Just 22 and recently married, he was called up to the artillery in 1967, after his younger brother had already joined the regular artillery regiment. Following several months of training, including specialised jungle courses (which the Americans often lacked), he found himself on a chartered Qantas plane with the rest of his company.

Laughing now, he remembers that they had to wear brightly coloured holiday shirts, because they were on a civilian flight. That same night, the airport where they were billeted was mortared by the North Vietnamese forces. It was a rude awakening for many of the young men. Speaking quietly, Ray says: "Within 15 hours of leaving Australia I was in a warzone."

Spending some three months of his seven-and-a-half month tour manning guns at the Task Force headquarters, Ray remembers that: "The guns worked every night; always working, always firing. You might fire a mission of 50 or 100 rounds of ammunition at a time, maybe with just a five minute break between missions." As the Australian and American patrols called in for support, Ray and his men often worked through from 8pm until four or five in the morning. They knew that their skills often meant the difference between life or death for the men caught out in the jungle.

It was a punishing schedule. "You would have your day's work, then go on guard duty. And then you would snatch some sleep in your 'pit' (a dug out trench), two hours on, four hours off. There was no real break. Then we'd have the morning and evening 'stand to', when everyone had to be alert for an attack." How many hours sleep would he get? "Four hours if you were lucky."

Still, he says, pausing to collect himself, working on the Task Force was preferable to the jungle patrols. These would be sent in on foot or dropped by helicopter, behind enemy lines, to 'sweep' a designated area. Ray's job was to join these men and call in artillery support, as well as fight as an infantryman.

"You would patrol an area, sweep through and clear it out," he says, almost matter-of-factly. The patrols could last up to two weeks, often laying night ambushes for enemy conveys and supply routes. Getting involved in firefights was "like a symphony orchestra with all the instruments playing at once...the noise is unbelievable, the din that's kicked up by chattering machine guns, and rifles and grenades. You get on another plane, if you like, all your senses heightened, finely tuned."

"We had some good laughs occasionally," he remembers, falling back into his old Australian accent, "but there were a lot of shitty times too. Ambushes, working under fire. I used to hate night ambushes in particular." He draws in a quiet breath to compose himself.

"One time we were out for a week and lay in an ambush position for a couple of days. Then they came down the road, about 30 Vietcong (guerrillas) - and we blew them away." His tone is deadpan, matter-of-fact again. "It was dark, it was nighttime, and they got in the killing zone and we just blew them away."

"Once the killing is done and they're there and dead, you stay in your position and let the noise settle. And then I saw the woman and children. Bodies were all over the place. There was one in particular, a pregnant woman split wide open by an M60 machine gun, opened up like a big slab of beef. Not very pretty. But she was the enemy, she was with them, and that was it."

Mike Hitchcock, another British veteran who fought with the Australian's long range reconnaissance Tigers Battalion (and who sadly died of cancer in 1998) told me how it felt to be such a killer.

"I just let rip and at that stage thought I was opening fire on a soldier. But then you see something roll down in front of you and you realise what you've done."

"First comes the stillness. You've been moving at an incredible rate, even though it seems like slow motion, and then nothing , but nothing, is said for about two or three seconds. Suddenly, you get up. With that, two things happen - you're ecstatic that you survived; then you walk up to what you've done - the incredible destruction you've visited on another human being - and emotionally, you're dead."

"You look down upon this 'thing', the body, as a lump of meat or an object. Until you have to touch it. Then you see something. Like with this girl. When I rolled her over her long hair came down. And then all of a sudden the feelings start coming in and you cannot help but think 'what have I done...what have I done?' Then you think 'Christ, are they really the enemy or just innocent people going through?'"

"Then you look for the weapon and you find it, and there's a great sigh of relief. After that, you think - because of your upbringing - 'this person had a family and friends' and you have now stopped that. Then it hits you and you start shaking...it took me a long time to get over it. I was shaking and howling like a baby for a week afterwards."

"Why? Because it was a girl for a start; a kid secondly; thirdly and most importantly, everything that I had been taught in my life, morally, just went down the drain. Totally. In one instant. The whole thing lasted maybe 20 - 25 seconds. And that 25 seconds changed my life completely."

"They shouldn't have been there. But they were, it happened, and what more can you say? After the first time, you don't shake anymore."

Veterans like Ray and Mike would develop a dark humour to cope with these traumas, joking that they didn't need to worry about the bullet with their name on it - just the one that said 'to whom it may concerns'. They also turned to alcohol. First in Vietnam itself, then when they got home. "Nearly all of us reverted to alcohol as a way of damping down the problems," Ray laments. "I used to go through booze like it was going out of style."

For Ray, the biggest changes occurred only several years after his return. "It was only later, after bringing up the children, going back to work, back into society, that something triggered it. My life was mundane, routine - and then it hit me."

"My first wife wanted me locked up, put in a mental hospital, she thought I was mad." Why? "I was having nightmares, I wasn't sleeping, I was looking for physical outlets to take away the stress. I had to be occupied. I couldn't sit still."

He kept recalling the time he had to literally crawl over dead bodies as he searched a North Vietnamese tunnel complex, armed with just a pistol and torch - he shudders at the recollection - or waking up to find a claymore mine had been placed in his sleeping pit. He ended up thinking of ways to kill his wife, and believes that his behaviour at the time - in the mid 1980s - nearly cost him his relationship with his children. It was these thoughts which eventually prompted Ray to seek help, from veterans' counselling services in Australia.

Yet few men like Ray initially received counselling for their problems - classic symptoms of Post Traumatic Stress Disorder (PTSD). Mike Hitchcock had a traumatic breakdown and Ray adds that: "We flew out (of Vietnam) and were back in Australia in 20 hours. Back into civvy street, no debrief, no welcome home parade, straight off the plane and that was it. And they expected you to fit straight back in."

The wounds were psychological, not physical. "I came back with my arms and legs, but you feel such a fraud that you didn't get killed and you weren't wounded. At least if you had your leg blown off, people could say that's why you're this way. But they stand there and look at you and say you look healthy. They don't understand."

When he returned to England and remarried, he spotted saw a newspaper advertisement for a unique organisation called Combat Stress. Formerly the Ex-Services Mental Welfare Society, set up during the First World War, Combat Stress deals with those suffering battlefield trauma. Ray went on one of their residential courses, and is currently undergoing long-term therapy with the organisation.

Now Ray says he is a "do-gooder, someone who will help somebody if they have problems." He studies military history, surrounded by reams of books in his study, and enjoys life with his wife Marian, a university lecturer. But he still can't join an organisation like the British Legion, because Britain was not 'officially' involved in the Vietnam conflict. And the memories linger on, no matter what counselling he gets.

"I was a civilian doing a killing job," he reflects. "The thought afterwards that I went in there and killed people - I killed children - made me think 'why?' I'm supposed to be a Christian, I'm not supposed to do that," he says, fingering the cross around his neck. "Then you come home and get spat at, for being a murderer and a killer. And your friends and family just want to forget everything, like turning off an episode of The Archers. And that's hard."