The police should consider changing the way it deals with criminal cases involving members of the Royal Family in the wake of the collapsed butler trials, an internal review has concluded.
Paul Burrell's case attracted media frenzy
But no "radical" changes are needed to police tactics, the report said.
There was outrage after the collapse of expensive trials involving Paul Burrell and Harold Brown.
Detectives were criticised after Mr Burrell was cleared at the Old Bailey in November of stealing from Diana's
His trial collapsed when it emerged he had told the Queen after
Diana's death that he had some of her possessions for safe-keeping.
Police had failed to establish this earlier and they were also accused of misleading the Prince of Wales by saying Mr Burrell had tried to
sell Diana's belongings.
The prosecution of Mr Brown and society jeweller Jan Havlik collapsed at the
Old Bailey in December.
Perfection is a worthy goal but in all areas of human endeavour it is elusive
The total cost of the trials was estimated to be £5m.
The conclusions of the report - which was aimed at learning lessons rather than apportioning blame - are unlikely to appease critics.
It concludes with the remark: "Perfection is a worthy goal but in all areas of human endeavour it is elusive."
Most of Bill Taylor's 10 recommendations in the report relate to general police procedure, but the first suggestion is that there should be changes in the way royal cases are investigated.
Metropolitan Police Commissioner Sir John Stevens welcomed the findings of the report, saying there had already been changes made.
He added: "Although superficially these were supposedly 'intrinsically simple' cases, in reality they were complex, difficult and challenging."
Sir John said much of the speculation relating to relations between the police and the Royal Family had been "ill-informed".
The internal review said another review should be set up to look at the way Royal cases were handled.
Among the reforms suggested are for detectives to have one point of contact in royal households from the start of investigations.
A new review should also look at how to make sure officers know about the unusual structure and practices of some royal households.
Scotland Yard's inquiry was carried out by Mr Taylor, former Commissioner of
the City of London Police and head of Her Majesty's Inspectorate of Constabulary
When the internal review was launched, Glen Smyth, of the Metropolitan Police Federation, said police officers had produced "compelling and persuasive evidence".
But they could not have known the Queen would intervene with dramatic new evidence which halted the Burrell trial, he said.