Donations of books, buttons and old brooches to the children's programme, which is celebrating its 40th anniversary, have raised enough money to buy 21 lifeboats.

Torin Douglas on Blue Peter's lifeboat appeals through the years

The RNLI said Blue Peter vessels have now been launched 3,109 times, saving 869 lives.

At a birthday dinner, Lieutenant Commander Brian Miles, director of the RNLI, said: "Your ability to inspire whole generations of young and not so young viewers has made you without question the RNLI's single most influential supporter over four decades.

Action stations: The RNLI says Blue Peter is a "dear friend"

"You are seen as a dear friend whose destiny is somehow linked to ours.

"Long may you flourish and long may we remain friends."

The programme's association with the charity began in 1966 with the first lifeboat appeal, where children collected paperbacks - enough to buy four boats.

Modern lifeboats launched by Blue Peter

Ronald Neil, chief executive of BBC Production and an executive committee member of the RNLI, said: "I am proud that the BBC has supported Blue Peter over 40 years so that successive generations of children have been able to save lives though their own efforts.

"And I am delighted that Blue Peter had the inspiration to choose to support the RNLI all those years ago."

Blue Peter stars of yesteryear rolled back the years on Friday by returning to the BBC One show for a live celebration on its 40th anniversary.

Daredevil: John Noakes dropped in for the 40th anniversary celebrations

Leila Williams, the first presenter of what is the world's longest-running children's show, was among those who joined in the fun, together with Valerie Singleton and Peter Purves.

Others who sent messages of support to the programme included Elton John, Rolf Harris and teenage pop stars Cleopatra.

Vintage clips, including the 1969 incident in which a baby elephant ran amok in the studio, were aired.

To round off the show they sang a chorus of Happy Birthday and cut a cake.