LONDON (Reuters) - Previously unseen footage of Britain's Queen Elizabeth as a young girl before acceding to the throne will feature in a new documentary airing at the end of this month, Buckingham Palace and broadcaster BBC said on Saturday.

       The May 29 programme, drawing from home movies in the queen's personal collection showing life as a princess, will precede celebrations for her seven decades as monarch.[L5N2WY572]

       "This documentary is an extraordinary glimpse into a deeply personal side of the Royal Family that is rarely seen, and it's wonderful to be able to share it with the nation as we mark her Platinum Jubilee," said BBC history commissioning editor Simon Young.

       Producers viewed more than 400 reels of film, including behind-the-scenes recordings of state events, and have dipped into more than 300 speeches she made, the BBC said.

       Among the footage is a beaming Elizabeth showing off her ring from husband Prince Philip, who died last year aged 99, before their engagement was made public. The queen is 96.

       (Reporting by Michael Holden; Editing by Andrew Cawthorne)