Today marks the 25th birthday of an invention which has changed humanity forever, and created a new virtual world within a generation.

There was no birthday cake yesterday, but you could have been forgiven for thinking a celebrity had just shown up at the Science Museum.

Crowds of school-children passed by with barely a glance - understandable given the uninspiring sight of an old computer. For the Ne XT cube is the machine on which the World Wide Web was created by British computer scientist Sir Tim Berners-Lee.

The only hint of its importance a tattered white sticker with the warning: "This machine is a server: DO NOT POWER IT DOWN!!

" It may be hard to believe now, but the worldwide web did not exist 25 years ago - until Sir Tim invented a way of using networks of computers to talk to each other.

Yet there was no initial grand ambition to emancipate the world through freedom of information for all.

The beginnings were much more mundane: an attempt to improve communication between the thousands of scientists involved with Cern, the European Organisation for Nuclear Research, in Switzerland.

Sir Tim was a 34-year-old physics graduate working as a software engineer at Cern in 1989, when he wrote a paper simply titled "Information Management: A Proposal".

It stated: "the hope would be to allow a pool of information to develop which could grow and evolve with the organisation and the projects it describes".

Ironically, the aim was envisaged as "a universal linked information system" where "generality and portability are more important than fancy graphics techniques and complex extra facilities".

It was initially damned with faint praise, his boss Mike Sendall writing "vague but exciting" on the cover.