Fourth wife Sally Burton had lent the diary

Sally Burton - the actor's fourth wife - lent the BBC a number of documents in March for use in the production of a documentary about her late husband.

Among the items was a diary which recorded the actor's thoughts in 1965, the year after his first marriage to Elizabeth Taylor.

It appears the documents were left in an unsealed box in a locked cupboard at the BBC's offices at White City in west London.

It was two months ago that they were discovered missing.

The life of one of Wales's most famous stars came under scrutiny back in July during a new documentary on the actor's life.

The diaries recorded thoughts of Taylor

The BBC programme used excerpts from his private diary which revealed how Burton felt the strain of being one of the biggest names in Hollywood, and even began to despise acting.

Burton - widely regarded as one of the greatest actors of his generation - was born in 1925 in the south Wales Valleys mining village of Pontrhydyfen.

His real name was Richard Walter Jenkins and he took his professional name from his old school teacher Philip Burton, who had a great influence on his life.

Burton's personal life - which included twice marrying Elizabeth Taylor - was almost as celebrated as his stage and screen roles.

He died in 1984 at the age of 58 in Geneva, Switzerland.