With the help of Kylie Minogue, Doctor Who was busy announcing the future of television last week. Fresh from winning an audience of 12.2m on Christmas Day, the Time Lord reappeared later on giant city-centre screens promoting a new service from the BBC called the iPlayer.

He was a suitably time travelling messenger - because the days of the fixed television schedule, when viewers had to accept what broadcasters served up at set hours, are numbered. The iPlayer allows you to watch programmes online up to seven days after they are broadcast – and it is just one of several similar systems heading for critical mass.

Sky offers its Anytime service that allows viewers to watch programmes on televisions or computers at times of their choosing. ITV and Channel 4 are joining the fray.

Next month Apple is expected to confirm a deal with Fox, the movie studio owned by News Corporation, parent company of The Sunday Times, that would make Fox movies available for rent digitally through Apple’s iTunes Store. Rivals, including Disney, already sell television shows including Lost and Desperate Housewives via iTunes.

Although sales have been modest, momentum is gathering as broadband becomes ubiquitous. The looming marriage of television and broadband promises a grand unified theory of everything for broadcasting, allowing you to watch whatever you want, from wherever in the world, whenever you like. Eventually it will be like iTunes, but for television.

“This really is a tipping point,” said Jody Haskayne, a spokeswoman for Tiscali, the broadband, telecoms and television supplier. “It’s an even bigger evolution than the one you have seen in music.”

Simon Wood, a media executive in London, is one of the converts to the new world of internet television. He logs on to websites that supply news, television shows and films from around the world. “I can get news and US shows that haven’t been broadcast over here,” he said. “It’s useful if you are into specialist subjects or if you want to catch up on things.”

Wood is tapping into one of two distinct strands of what is loosely called “internet TV”. The first is to watch material over the web on your computer; the second is to have shows sent straight to your television via the broadband telecommunications network.

Websites such as worldtvpc.com list hundreds of television stations around the globe. A few mouse clicks on Friday brought up a Cuban channel showing a drama, an Iranian station discussing Al-Qaeda and a French station broadcasting a programme in English about a reggae singer.

Although some stations require subscriptions or passwords, others are free. However, there is a limit for most viewers to the attractions of Strictly Come Yakking from outer Mongolia.

More important is the way traditional UK broadcasters are embracing the web, no longer seeing it as an enemy but as an ally. Bebo.com, the most popular social networking website in Britain, is cooperating with mainstream broadcasters to carry clips of programmes.

In a similar way myspace.com has linked with NBC, the US broadcaster, to provide a television service. Broadcasters see such moves as a way of reaching the “web generation” who prefer to spend time networking online rather than watching traditional television.

ITV.com, which offers its own “catchup” service, said: “We have gone for a free, advertising-funded model. You click and watch, it’s served directly to you. There’s also an archive of films and programmes you can choose from.”

What’s not to like? The main problem is that the technology of the web does not yet match the quality of television. When you call up a video or programme via a website, it tends to be shown on a small screen; if you expand it to full size, the quality can be woeful.

That is where the second strand of “broadband TV” comes in. Media companies can send films and other programming over the broadband network direct to your television, rather than computer. The quality is far superior.

BT Vision has 70,000 people signed up to such a service, which requires a simple set-top box. “You get Freeview plus you can stream and view a wide range of other programming when you want,” said Adam Liversage of BT. “The content is coming straight off our own servers, so it’s fast and simple.”

Tiscali is another player forging a marriage of media. It is best known for providing broadband internet access but it is fast moving into television. “We’ve got more on-demand programming than any other service,” claimed Haskayne. “Movies, sports, documentaries, entertainment – you can go and say: I want to watch a whole series of, say, Sex and the City or Spooks.

“What I use it for most at home is catchup – you can watch what you want when you want.”

Jeff Jarvis, a former US television critic turned internet pundit, believes that one day all television will be delivered this way. “The era when people were prepared to watch TV on some network’s schedule is over,” he said. “The power used to reside with whoever controlled the broadcast tower, but those days are gone.”

Nor does he believe that in the future most programmes will be watched on a television set, despite the advantages of bigger screens. He has just finished watching the last season of Weeds, the US comedy about a dope-dealing suburban mum. “I want to watch what I want, when I want, where I want,” said Jarvis. He did – on his iPod as he commutes.

To Richard Collins, professor of media and sociology at the Open University, the new television age is “broadly positive from a consumer perspective”. Viewers will get an enormous choice. The downside is that the frontiers and economic models underpinning existing regulators and broadcasters will be swept away.

Collins points out that Joost, a nascent internet television service, offers a host of on-demand programmes distributed from servers in Amsterdam, London and New York. “So it’s hard to say what the country of origin is and who should regulate it,” he said.

Other factors also change the landscape. The costs of production are so modest that almost anyone can have a go at making a programme or starting their own TV station. That is what Justin Gayner, a former freelance journalist, has done.

After a chance conversation in a pub, via a modest investment in equipment, he started channelflip.com, his own television station. “In our first month our shows have been watched 170,000 times by 70,000 viewers,” he recently reported. In America, Will Ferrell, the comedian, has launched his own comedy channel, funnyordie.com, on the internet.

Some traditionalists may fear that such ease of entry will erode standards and lead to dumbing down. But Collins is optimistic. “I'm not convinced by the doom and gloom stories,” he said. “The undermining of existing economic models doesn’t mean that new models that can sustain quality won’t emerge.”

That leaves only one problem with this bright new future of television coming to you on the information super-highway: there may be one hell of a traffic jam. Films and television are like juggernauts thundering down the telecoms network into your home. They need space and Britain does not have much of it.

Most homes here still rely on the copper wires of the old telephone network to deliver broadband. It provides a far slower service than fibre-optic cable. Experts are working on technological tweaks to make the system faster, but ultimately the brave new world of any time, anywhere television may require something fairly basic: a new cable.

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