The BBC has revealed that Keeping Up Appearances is its most popular programme internationally.

Despite being only 25 years old, the hit 1990s sitcom has been bought 992 times by channels in other countries - more than any other BBC programme for at least 40 years.

The hit sitcom ran for 5 series in the early 1990s, starring Patricia Routledge and Clive Swift. A prequel entitled Young Hyacinth is understood to currently be in development.

Commercial arm BBC Worldwide released the data to mark the 40th anniversary of its Showcase events, in which formats owned by the corporation and a number of independent production companies are promoted to executives from international TV stations to buy, or to licence and remake.

The company explains: "It's not just historic interest from buyers that has made Keeping Up Appearances a record breaker, it continues to appeal and has recently been acquired by broadcasters in Australia, Bulgaria, Ireland, Nigeria, Denmark and Latvia."

Creator and writer Roy Clarke says: "The Old Girl keeps on raising and ridding the dust. I think the secret to her wide fan base is that everyone knows a Hyacinth. It appears that she's an international phenomenon. Wherever you are it seems there's a Hyacinth next door, or just down the road or in the family. Great fun for half an hour as a spectator - but permanently? I shouldn't grumble. Bless her she's been good to me."

BBC Worldwide Showcase began in a meeting room in The Old Ship Hotel in Brighton in 1976 with 25 buyers present and has grown to the world's biggest single distributor trade fair, regularly attracting more than 700 international buyers.

Since the inception of the Showcases, BBC Worldwide has sold programmes to more than 200 territories across the world - almost every country on Earth.

The second most-bought programme has been revealed as Sir David Attenborough's The Life of Mammals, with 958 acquisitions. The most purchased drama series is the first revived series of Doctor Who from 2005, starring Christopher Eccleston, with 629 sales.

The company also announced that the most bought Factual Entertainment series is Top Gear Series 9 from 2006, which has clocked up 282 sales in countries ranging from the United States of America to Albania and Iran.