VIRTUAL worlds are a global industry worth tens of millions of pounds a year.

Eleven million people pay an annual fee of $15 – a bit less in poorer countries – to play the adventure game World of Warcraft.

Twenty five million players have at some point entered the kids’ on-line universe Habbo, and players spend an astonishing average of 38 Euros a month buying imaginary possessions for their on-screen characters.

It is a 21st century money-spinning phenonomen, but the West Bergholt man who invented the ancestor of today’s virtual worlds did not see a penny for his trouble.

Dr Richard Bartle was a young undergraduate at Essex University in 1978 when he devised Mud – short for the rather-less-catchy technical term Multi-User Domain – with help from fellow student Roy Trubshaw.

The text-only game took inspiration from the Lord of the Rings and Dungeons and Dragons, but was a far cry from the spectacular graphics of World of Warcraft, with players relying on written messages that spluttered across the screen like football results on a sports news channel.

Crucially though, it was played by thousands of people in different countries, and had the magic ingredient of unpredictability.

If a player typed in “I want to go in the tavern and drink a glass of mead,” a message would flash up “you are in the tavern drinking a glass of mead”. But if they were carrying a lighted fire torch, and someone in the tavern had a pouch of gunpowder in their pocket, the player would instead be informed that they had perished in an explosion.

As time went on, players devised ways of killing their gun powder-carrying enemies and a game began to evolve, taking on a life of its own.

Mud’s inventor says he does not regret his decision to make his game available for free, as without such a large number of players, its full potential may never have been realised.

He said: “In America people were coming up with similar ideas at about the same time but they tried to commercialise it so they kept their expertise to themselves.

“I used to give away the source code to Mud so people could write new bits of programming for it themselves.

“As we’d given ours away for free, others did the same for free, and there was this flowering of creativity.

“By the time the games industry decided there was money to be made and wanted people to do programming for commercial games, there were only a handful of experienced people on the American projects, but thousands with experience of Mud.”

Dr Bartle, 49, now an Essex University lecturer, says Mud’s claim to have spawned the virtual worlds of today is made on the same basis as Scotland’s claim to have invented golf.

“Golf was invented several times in different countries, in some cases centuries before the Scottish version, but the golf played today was invented in Scotland,” he said.

“In the same way, there were several inventions of virtual worlds but the ones played now are all descended from mine.”

He’s in no doubt he is directly responsible for the growth of online universes, inhabited by more players than some medium-sized countries.

So what does Dr Bartle make of his legacy?

All over the world, grown men and women are devoting hours each evening to online escapism instead of interacting with their families.

Virtual worlds have been implicated in a string of marriage break-ups, most infamously that of a Newquay man who was divorced after his wife found his online character in a compromising position with a female character in the game Second Life. Though he has himself been happily married for 24 years to Gail, 47, the mother of his two daughters Jennifer, 18, and Madeline, 15, Dr Bartle admits Mud divorces probably outnumbered marriages between players by about ten to one, due to the time people devoted to it.

But he insists, on balance, his gift to the world has made it a better place. He said: “Being in unusual, dangerous situations can help us learn about ourselves.

“You can put yourself in those situations by going to fight in a war, but you might get shot, or you could go exploring to the North Pole or something, but you’d need a lot of money.

“An ordinary person is now able to get the same kind of experience in a virtual world. Virtual worlds help people to be themselves.”