VIEWERS switching on the BBC's newest channel 40 years ago were left in the dark. Never mind the promise of the first television pictures in colour to come in a few years, BBC2 couldn't manage anything but black on the opening night on April 20, 1964.

A power cut left people in London and the South-East, the first parts of the country to receive the new channel, staring at a blank screen instead of the musical Kiss Me Kate with Howard Keel.

Faced with operating by candlelight, BBC bosses abandoned the opening until the following day, when Playschool became the first programme to be broadcast on the channel in its entirety.

Dubbed "the thinking man's channel" - pretty insulting to viewers of BBC1 and ITV when you think about it - BBC2 aimed to provide an alternative to the other TV stations.

You'd be hard pressed to see the difference between those three channels these days, with their common mix of dramas, documentaries, quizzes, lifestyle and property shows.

BBC2, in common with everyone else in the multi-channel TV world, can't afford to be too different or out-of-step with what people want to watch. If it does find a success, the chances are it will be pinched by BBC1, as happened with shows like Have I Got News For You?, Ground Force and The Office.

In its turn, BBC2 is providing an audience for shows that have first seen the light of day - but few viewers - on BBC3. Acclaimed comedy shows Little Britain and Nighty Night, as well as The Alan Clarke Diaries, have transferred from 3 to 2.

This seems far removed from BBC2's original remit that put the accent on arts, documentaries and education programmes. All very highbrow, although it took a drama like The Forsyte Saga and the start of the first regular colour TV service in Europe in 1967 to make people switch to BBC2 in significant numbers.

On its 40th birthday, the inclination is to look back on BBC2's ground-breaking successes - science and history programmes like Civilisation and The Ascent Of Man; sports shows like Match Of The Day and Pot Black; dramas including Boys From The Blackstuff, and Our Friends In The North; and comedy shows such as Fawlty Towers and The Office.

Whether it can continue with what the BBC press release describes as "innovative and ground-breaking programming" is open for debate, as the battle for ratings and justifying the licence fee intensifies.

On the channel's 30th birthday, the then-controller Michael Jackson spoke about BBC2's experimentation, of looking for new audiences, of not just doing what's tried and tested, of doing things differently.

The current BBC2 controller Jane Root, soon to leave for a new job in America, believes the most enjoyable thing about the channel is that "it brings surprise, sophistication and innovation" to a range of things.

"It has always been famous for creating both popular comedy and thought-provoking programmes," she says. "That sense of variety has been there all the way through the channel's history."

Brave words but Channel 4 and, increasingly, five schedules are interchangeable with BBC2's. Only the titles are different, the content is the same.

Happy Birthday BBC2 tonight recalls the past 40 years on the channel. The cast of Dead Ringers interrupt from time to time with their impression of how BBC2 has done, if only to prove the channel's sense of humour is intact.

Everyone will have their own favourites, but here are ten of not necessarily the best, but certainly memorable in their own way, BBC2 programmes: