A sprawling archive of Sir Edward Heath's private papers will be examined as part of an inquiry into alleged sex abuse that is expected to cost millions, according to reports.
The 4,500 boxes of material currently held at Oxford University's Bodleian Library are to be read by civilian investigators recruited by the police, it is understood.
Among items said to be in the archive acquired by the library in 2011 are diaries and personal letters belonging to the late Tory prime minister.
According to The Times the examination of the boxes is expected to take a year, as their contents have not been catalogued.
Detectives are probing several allegations of abuse against Sir Edward, who led the Conservative government between 1970 and 1974, and died aged 89 in July 2005.
Wiltshire Police are also said to be trying to contact Sir Edward's staff and guests at his home in Salisbury.
A force spokeswoman said: "Our investigation is ongoing and we are conducting a number of enquiries. We are not prepared to discuss any details of the investigation."