As Big Ben chimed midnight at the turn of the millennium, there were just five terrestrial television channels and 102 digital channels, which were accessed by only about a quarter (6.4 million) of the UK's TV homes.
Fast-forward to 2007, however, and the picture is rather more complex. Consumers now have the choice of 450 digital channels, and 81% of homes have digital access - a figure that media agency ZenithOptimedia forecasts will rise to 100% by 2010.
Andy Barnes, sales director at Channel 4, says: "Until the year 2000, TV was largely the same as it had been since the 1960s. But the rate of change over the past two years has equalled that of the past five, and it is only going to get quicker."
Most radically, consumers can now watch TV when and where they like, following the introduction of IPTV, broadband TV - which has been launched by all the major broadcasters - and time-shifted services such as the spiralling number of +1 channels and PVRs such as the Sky+ box, now a fixture in 12% of UK homes.
Thinkbox, the television marketing body for all UK commercial broadcasters, anticipates there will be one million IPTV households by 2010, and reports that 38% of the population has watched TV via broadband, with 34% having downloaded TV programmes or clips (60% among 18 to 24-year-olds).
Today's video-on-demand culture also puts consumers in the driving seat as to the choice of viewing platform. In September, more than 340,000 households used the Sky Anytime service, available online, on PCs and on mobiles, each week.
Tess Alps, chief executive of Thinkbox, says: "The 1990s brought multichannel TV, but from 2000, people have had more control over their viewing: they can save programmes and watch TV at different times and on different devices."
Alarmists have been quick to predict the demise of TV advertising, in a climate where supply far outstrips demand and airtime is at its cheapest since the early 1980s.
As the argument goes, if viewers can skip through time-shifted TV as their mood takes them, surely they will also fast-forward through all those intrusive ads?
A new golden age
On the challenges facing the traditional 30-second spot ad, Adrian Swift, director of television at digital production company etv, warns: "The problem for planners and buyers is that a traditional TV ad break is now 50% less effective."
However, the majority of the media industry vehemently denies that traditional TV has met its maker. C4's Barnes says: "There is much talk about the death of TV and it's not true. The notion that the internet is killing TV is madness."
Nick Bampton, managing director of Viacom Brand Solutions, which sells advertising for channels such as MTV and Nickelodeon, adds: "The internet is playing a massively important part in growing our TV business; we are on the cusp of a golden age for TV. Our internet business for 2007 is set to be up 100% year on year and this is only because of the existence of TV: all that money is integrated."
Industry figures support their optimism. ZenithOptimedia forecasts that TV ad revenues will stabilise at 0% growth during 2007 and will rise by 2% over 2008 - an encouraging upturn on the 5% drop in 2006.
Thinkbox reports that the internet has not displaced time spent watching broadcast, linear TV. The average UK viewer watched 2.26 hours of commercial TV a day in the first half of 2007, marginally up on the average first-half viewing hours since 2002.
And studies have shown that owning a PVR actually increases broadcast viewing by 15%, resulting in a net increase in the number of commercials viewed.
What is undeniable, however, is that the halcyon era when four channels automatically commanded multi-million mass audiences - and TV traders grew fat as ad revenues climbed by 15% each year - are but a distant memory.
As Gary Digby, managing director of ITV Customer Relations, says: "In the four-channel environment, we had shows that attracted 17 to 20 million viewers. But to attract 10 to 11 million viewers in a 400-channel environment is a far greater achievement."
Etv's Swift comments: "The wind has shifted and the industry must adjust its course to deal with the change. Television audiences have moved much faster than the media agencies, the broadcasters or even the internet guys. The biggest challenge is to find out where the audiences have gone and what they are doing there."
The priority for broadcasters, according to Thinkbox's Alps, is to prioritise high-quality content - appointment-to-view programming such as The X Factor and live sport - while finding the money to invest in taking the content to new platforms.
She says: "The challenge is to persuade the industry to invest in new forms of TV with new money - the viewing is in addition to the linear schedule, not instead of."
ITV's Digby agrees that content must be the focus for broadcasters, given the increasing disconnect between television programming and the device it is viewed on. He says: "Content will drive the market, because fantastic shows are the only thing consumers care about. But you need to make sure you own that content so that you can maximise revenues from distribution rights."
Content versus distribution
The drive at the BBC is to strike the right balance between investment in content creation and investment in technology and distribution. The "big strategic decision", according to Ashley Highfield, director of new media and technology at the BBC, is whether the BBC gives its content away to platforms with "strong and growing audience bases", such as YouTube, or offers the content itself from its own website.
He says: "In practice, this means we will put a wide range of clips on to YouTube - and we have already reached three million users - but we will also try to bring the users back to bbc.co.uk to watch the full-length programme using the iPlayer."
Meanwhile, advertisers must invest more of their budgets in sponsorship deals and ad-funded content, now that media watchdog Ofcom is regulating with a lighter touch. Swift, who claims that sponsor bumpers have become "part of the PVR viewing experience", says: "There is now more value for advertisers in being involved in creating shows and funding or part-funding content, particularly for mobile and internet TV."
On the opportunities for developing new advertising models, Nick Milligan, managing director of Sky Media, says: "We have developed totally new pre- and post-roll slots (for Sky Anytime on TV) that encourage the advertiser to take the viewer on a journey from the beginning to the end of a selected programme."
Innovations in the red-button interactive world are no less fast moving. Last month, Sky introduced video advertiser locations (VALs), developed so that advertisers can offer viewers the chance to see long-form video content at the touch of a button. In addition, Sky is close to making "bookable advertising" available in Sky+ homes: an opportunity to download a long-form ad, just as one would a programme.
If sales of HD televisions are anything to go by - there are currently 2.4 million HD-enabled sets in the UK - there will always be a place for the traditional TV set in the corner of the living room, even if it is an exotic PC/TV hybrid.
However, the multiplying number of viewing platforms will offer consumers ever-more choice and control. Milligan adds: "With this innovation will come better-targeted and more engaging advertising opportunities. Those that are alive to the possibilities will enjoy the next part of this exciting journey."