Each of the four volunteers, dressed only in a dressing gown, have been given a computer, £500 and a credit card - before being cast away on a virtual desert island. Now they must feed, clothe and amuse themselves through the Net for 100 hours.

Technology Correspondent Christine McGourty reports on an unusual endurance test

After one day in their central London "desert island", they have already managed the first, and most important task by taking delivery of their first food rations.

But the hosts for the experiment, Microsoft, were forced to admit that the orders were put in before the experiment started.

"We let them order food for today last week, because there's always going to be a lag between ordering and taking delivery," a spokesman said.

"We didn't want them to starve - and the orders were made via the Internet, so they were still in the spirit of the event."

The number of Internet users is rising rapidly

The four volunteers, aged from 30 to 67, may have had trouble finding the time to put in their food orders this morning in any case.

Their only contact with the outside world is through e-mail and chat groups - but within a couple of hours, Robin Katz, Martin Kennedy, Emma Gibson and Glyn Thomas received up to 50 e-mails each, and the chat rooms had become clogged.

Webcams, set up to watch the four as they attempt the first truly virtual lifestyle, were turned off for two hours in the afternoon to give the four a break.

The group, aged from 30 to 67, volunteered after spotting a newspaper advert placed by organisers msn.co.uk, Microsoft's Internet arm.

It is expected that by the end of this year there will be more than nine million users of the Internet in the UK, with predictions of retail revenue topping £5bn by 2003.

Microsoft plans to repeat the experiment in a year to see what advances have been made.