Good old days? Some say the show summed up an era

Many describe the 1970s as the programme's heyday, when its Thursday night slot would attract 10 million viewers.

An appearance on Top of the Pops would as good as guarantee a high chart placing when the new charts were unveiled the following Sunday.

Hairy Radio 1 DJs would introduce bands, while dance troupes Legs and Co and Pan's People kept teenage boys across the country entranced.

And it is that period of the show's history that is often thought of as defining an era - seen by some as unsubtle and unstylish, and by others as fun and uncomplicated.

The show has always struggled to keep up with the times since then, but has remained a vital part of music scheduling.

Radio 1 DJs used to present all shows

During the 1980s, Madonna gave us a taste of what was to come when she performed Like a Virgin in a pink wig, while two up-and-coming Manchester bands, The Stone Roses and The Happy Mondays heralded the appearance of Madchester on the same show at the end of the decade.

But for every moment that the show has memorably and successfully tapped into youth culture, there has been a performance that has become notorious for the opposite reasons.

In 1983, Dexy's Midnight Runners played Jackie Wilson Said in front of a giant picture of darts player Jocky Wilson. To this day, nobody quite knows why.

Many also remember Billy Bragg mumbling his way through She's Leaving Home because his lyrics were taped to the floor, and hidden by the dry ice, and All About Eve sitting in confused silence because their backing track failed to start.

Legs and Co provided visual entertainment

The show has not been recorded at Television Centre since October 1991 - in which time the show and the music world have changed.

At the time of the move, Bryan Adams was coming to the end of his record-breaking 16-week stint at number one, while KLF, Chesney Hawkes, Color Me Badd and Jason Donovan also hit the top spot in that year.

But so did U2, Cher and Michael Jackson - all artists who will also have releases in 2001 and will be featured on the one-hour special to mark the show's return to TV Centre.

Since 1991, the policy of having just Radio 1 DJs as presenters has been dropped, and its hosts have gone from Steve Wright and Bruno Brookes to Jayne Middlemiss and Jamie Theakston.

Dexy's: One of the most notorious mishaps

Producers also dabbled with the practice of forcing all the acts to sing live - it is now optional again - as well as moving the show to Friday nights and launching spin-off shows Top of the Pops Two, Plus and At Play.

The 1990s and beyond have also produced their fair share of memorable moments - the stage invasion when Nirvana played Smells Like Teen Spirit, 75 people buckling the stage during Fat Les's performance, Supergrass's Danny destroying the drum kit and Robbie Williams threatening Prince on stage.

And a new generation of stars emerged - Jennifer Lopez demanded "dozens" of dressing rooms for a recent appearance, according to the show's website, while R Kelly brought 43 bouncers and Busta Rhymes stayed in the studios for just 30 minutes but recorded three songs in that time.

The show has seen competition arrive in the form of scores more channels, the internet, video and DVD.

It is still shown in 80 countries, and it now attracts four million viewers per week in the UK - down from its heyday but still the most popular pop show on TV.