The series is seen as a way of bringing science to life

And BBC News is about to launch an interactive TV service to compete with that of Sky News.

After years of false starts, interactive television is starting to deliver some of the benefits its evangelists have long been promising.

Sky led the way, with its Sky Sports Extra service, offering a choice of camera angles for football, rugby, golf and cricket and a welter of statistical information.

Wimbledon

It extended the service to news - with Sky News Active, which provides a choice of stories, in video and text - and to film, with Sky Movies Active, which shows previews of films, reviews and cinema listings.

The BBC has also been an interactive pioneer.

Its Wimbledon service last year provided digital terrestrial viewers with on-screen facts and figures about the players and matches.

This year, it offered digital satellite viewers a choice of matches to watch - up to five different courts at a time - and several million viewers did so.

What happened when the dinosaurs disappeared?

Now, the BBC has produced the first interactive documentary series, Walking With Beasts.

As with all these developments, how much interactivity you get depends on which platform you are using.

Voices

Satellite viewers get a choice of commentaries - the standard Kenneth Branagh delivery, or a more detailed, scientific version spoken by Dilly Barlow, the voice of the Horizon programme.

They can also see extra video clips, including interviews with scientists and the programme-makers, and they can even watch the whole programme again 24 hours a day, for seven days after it was broadcast.

Terrestrial viewers, watching through ITV Digital, can read more information about the creatures, synchronised with the broadcast. And cable viewers can also see text information and discuss the programme on message boards.

Palaeontologists look to the present to understand the past

From 20 November, the BBC News Interactive service will give digital satellite viewers constantly updated news, sport and weather summaries - as well as extended coverage of live events.

And this year's Children In Need appeal will let digital viewers pledge money directly via their satellite and cable services.

But perhaps the most popular new interactive development will be the battle of the quiz shows - Mastermind versus Millionaire.

The Discovery Channel has mounted a heavy publicity campaign for its new Mastermind series, hosted by Clive Anderson.

Millionaire

Its digital satellite viewers will be able to play along with the General Knowledge round, selecting from four answers displayed on the screen, and registering their scores on a viewers' league table.

After several weeks, the top four viewers will be invited to take part in a viewers' final in front of the cameras.

Meanwhile, Who Wants To Be A Millionaire? - which, with its multiple-choice questions, could have been made for interactive TV - is about to let ITV Digital viewers play along at home for prizes.

From 24 November, the programme will be broadcast on the terrestrial channel ITV2, simultaneously with ITV1.

People who get high scores at home will qualify for a prize draw - though, sadly, not for a million pounds.