Who is Sir Alex Ferguson? Despite the reams of newsprint and hours of TV and radio broadcasts dedicated to the Manchester United manager's retirement, none of it has given me any deeper insight into the personality of the man. We hear over and again the jaw-dropping statistics about the trophies won, and the cliches – the hairdryer, the horses, one of the greatest managers of all time – but who can tell us anything really personal about Ferguson? If there is anyone out there, they are keeping quiet.

I call it the Manchester United mafia, led by Sir Alex Fergu-don. In 25 years of professional football, a period in which I have played Ferguson's teams on many occasions, I have never exchanged more than a hello and a nod with the man. Whereas a manager like José Mourinho will give you the time of day, Ferguson is unapproachable.

If there is a code of silence, Ferguson's players are bound to it. Despite being friends with Rio Ferdinand and Wayne Rooney, among others, I have never – ever – heard them say anything about Ferguson. All those hours of sitting around at England camps or on bus rides, and not once did any United players ever reveal anything to me about their team-mates, their dressing room or their manager. In an industry renowned for its gossip I find that extraordinary.

On one occasion I remember sitting with Phil Neville for a chinwag and, like a typical footballer, ranting about a team-mate of mine who I found annoying at the time. When I'd finished I expected Phil to reciprocate. But there was not a word. "What an absolute prick!" I thought, red-faced after pouring my heart out only for him to remain tight-lipped. But later I concluded that his approach was an exemplary – and clever – way to carry yourself through a career in football.

All the United players were the same, no one would ever say a bad thing about their team-mates. Even when the media reported chaos in the United dressing room – from the infamous pizza throwing to Becks' cut above the eye after Ferguson kicked a boot at him – there were no comments from the United boys. There were plenty of questions, of course. But their answers were only ever vague, or meaningless.

It all contributed to that sense of separation: there were United players, and then there was the rest of us. And I have little doubt that it was Ferguson himself who encouraged that segregation. For it was Ferguson who was the first manager to ban opposition players from entering the home players' lounge for a drink after a game. Until then post-match mingling had been a tradition. But while Ferguson famously enjoys a glass of red with rival managers at Old Trafford, he was quick to ensure there was no such socialising among his players. At the time the football fraternity was horrified. There was this feeling of "Just who do you think you are?" Little did we know.

At England camps United players kept themselves apart. They had a competitive ethos so extreme it was unlike anything we had ever come across. While a simple training drill of piggy-in-the-middle was usually understood as an exercise in which you worked together against the man in the middle, for United players it was an opportunity to catch each other out. I had never seen it played that way before. To talk about one individual player being competitive is unremarkable, but to apply the same label to generation after generation of players from one specific club is unheard of.

Everyone keeps asking whether David Moyes can control the United dressing room, but United players police themselves. Ferguson created an environment in which players would control each other, so that he didn't have to. The presence of Ryan Giggs and Paul Scholes was significant. Two players who had won more trophies than anyone else meant that there were authority figures in the team, whom younger players dared not question.

And wow, were they professional. While the likes of Rio and Wazza are very funny, very loud characters, they are very serious about what they do. I should know, I've been on the receiving end of one of Rio's tirades for some minuscule incident on the pitch. That's the norm at United, where anyone who steps out of line or makes an error can expect a verbal battering from their team-mates. United players just have that intensity about them. Sure, we are all professionals, but I have not heard other players sit at the back of the bus after a game and analyse the match in the way that Rio or Rooney do.

There is no doubt: Ferguson is revered as the supreme leader. A man whom the other football managers appear to be in awe of as they phone him up for advice, confiding in him their insecurities. Anyone who has tried to take him on in football has been crushed – from players who got too big for their boots only to be shipped out in the next transfer window, to managers who attempted to beat him at his specialist subject: mind games. As Kevin Keegan once found out to his cost, it took a brave man to think he could outfox Sir Alex.

No wonder then that even here in Iceland Ferguson is the talk of the town. Sitting with Hermann Hreidarsson and a group of fishermen before training on Friday morning, drinking coffee out of broken cups in their boat yard (you see how bizarre it is here), the conversation – in Icelandic – was peppered with references to United, Ferguson and Moyes. Just as I was giving up on trying to understand what was being said, Hermann turned to me, nodded and explained: "Moyes was here in Iceland for half a season, they say." Apparently he played for IBV for half a season when he was a youth player. I'll take that as a good omen. If I can emulate anything close to what Moyes has achieved, a manager deemed great enough to fill Ferguson's boots, I'll be a happy man.

David James has donated his fee for this column to charity