I was born in Clydebank, near Glasgow, where the famous John Brown shipyard used to be. But as I was growing up, the main employer in the area was the Singer sewing-machine factory. My father worked in the foundry there, and Mum looked after us. When she did go out to work, it was as a cleaner.

There were seven kids in our house. It was a two-up, two-down: one family in the top, another in the bottom. There was food on the table but we were pretty poor. As kids, that meant things like not being able to get an ice cream when the ice-cream van came round.

By my 16th birthday I'd already left school. I dreamt of being rich one day - I just didn't know how to go about it. The only thing that caught my eye was an advertisement promising a bright future in the Royal Navy. So, a week after turning 16, I signed on for 12 years.

For the first year I was based at a training ground near Ipswich. Then, in 1966, I was transferred to the cruiser HMS Tiger. By 1968, three years into naval life, I was serving on HMS Eagle, an aircraft carrier. I'd got to see a lot of the world, but I was disenchanted. I seemed to be spending most of my time in the boiler room or cleaning toilets. I'd also acquired a record for 14 minor offences including bad timing, drinking alcohol aboard ship and insubordination.

I had a week's leave in September of that year. On the night that I was due back, HMS Eagle was anchored off Lossiemouth, on the northeast coast of Scotland. The rule was you had to be back by midnight, and to get us onto the ship, a liberty boat was used to ferry people between the ship and the jetty. By about 11pm, there were quite a few of us waiting for it to arrive. It was cold and dark. Then we found out the liberty boat was waiting at the ship for some officers who were going to be seeing their guests back ashore after an on-board party.

Eventually the liberty boat arrived with them. I guess I must've been standing by the edge because my commanding officer (CO) got off, saw me and - poking me in the chest with his torch - said: 'Make a gangway.' I could tell he was drunk and he was showing off to the girl who was with him. I didn't like his attitude, so I turned around and said: 'Don't do that again.' He just looked at me. A mate of mine was standing next to me and I said to him: 'If he does that again, I'll throw him over the bloody side.' As far as I was concerned, this CO was a stuck-up public schoolboy with no decorum, no common sense and no guts. In fact, I'd already had runs-ins with him, so you could say we had a history. My mate said: 'I bet you £5 you don't.'

Hearing this, I didn't wait for the officer to say another word. I grabbed hold of his legs, lifted him into the air and literally had him upside down. I was just about to throw him over the guardrail into the water when a group of officers realised what was about to happen and jumped on me. They grabbed my arms and pulled me away. The CO didn't say a thing - he just looked terrified. Then the military police arrived, and before I knew it I was being taken aboard the Eagle and dragged off to one of the ship's cells.

The following morning I was told I was going to face a captain's hearing, then I would be court-martialled. I was kept in the cell for another three weeks until the ship docked at Rosyth, near Edinburgh. Then I was removed from the ship and taken to a room at the naval base, where I stood in front of naval officers and judges. Did I regret what I'd done? The answer was no. And I was prepared to accept the consequences. I was found guilty of showing violence to a superior officer and sentenced to nine months at Colchester detention barracks.

My mum had been particularly proud of me joining the navy, so I didn't want to let her down by telling her what had happened. But the whole affair hit the local headlines and she ended up seeing me on the TV news. I served just over six months of my sentence and at the end, although I was asked if I wanted to go back into the navy, I said no - I wanted out for good. Instead I went back home.

I was 20, I had no references, no qualifications and I was penniless. In one way I was back where I'd started. But in another sense I'd come a long way. I'd walked away from that whole naval experience realising that nobody else was going to stand up for me, or help me realise my potential. If I was going to succeed in life, then everything was down to me. Back home in Clydebank, I woke up realising that while I was not master of the seas, I was master of my own destiny. It was a major turning point. Thirty-seven years later, not only would I have made my first million, but I would have made my first hundred million.