The realms of inquiry - a collapsed trial, a claim of rape and backhanders

The four areas of the internal investigation into events and allegations surrounding the collapse of the trial of Paul Burrell:

1. Whether there was an improper cover-up of the allegations that a key aide to Prince Charles raped a royal valet.

George Smith, 42, a former valet, claims he was raped by an aide to the Prince of Wales in 1989 and was sexually assaulted by the same man, about six years later. Diana, Princess of Wales, taped his claims but the tape disappeared after her death. An inquiry by the Prince's solicitor, Fiona Shackleton, foundered after Mr Smith said he did not want to pursue the matter; Mr Smith, who suffers from depression and alcoholism, was later retired from the Palace. Sir Michael Peat, the Prince of Wales's private secretary, said yesterday the matter was reported to local police at the time, contrary to previous reports. But no action was taken because of Mr Smith's mental condition. Mr Smith repeated his claims in The Mail on Sunday at the weekend. The alleged attacker issued a statement on Sunday rejecting the accusations. It is claimed Prince Charles is paying the man's legal fees.

2. Whether there was anything improper in the conduct of the Prince's household over the collapse of the Burrell trial.

In the official version, the trial collapsed because the Queen failed to appreciate the importance of a conversation with Mr Burrell in which he told her he was keeping some possessions of the Princess; the Queen recounted her conversation to Prince Charles, who told police. It has been speculated the real reason was Mr Burrell's knowledge of the tape, which he might disclose in the witness box, naming the alleged attacker.

3. Whether any official gifts had been sold.

Mr Burrell's statement to police suggested Dianawas in the habit of selling her clothes to raise cash. Other newspaper claims have involved Michael Fawcett, an assistant to Prince Charles, as being involved in the "selling on'' of gifts. The inquiry will examine whether these claims involve official gifts, which are State property and cannot be disposed of.

4. Whether any members of staff had been in receipt of improper benefits or payments.

There have been claims Mr Fawcett received a £3,800 Rolex watch from an Arab prince for helping to organise an event involving Prince Charles.

Civil service rules, which govern royal employees, say gifts over £50 must be declared and usually handed over.

Sometimes they can be bought by the recipient at an agreed price.