Police investigating the death of an MI6 officer are to intensify their inquiries into his colleagues and work following criticism at last week's inconclusive inquest.
Met Commissioner Bernard Hogan Howe has announced detectives will have direct access to MI6 officers and material for the first time.
There will also be a review of forensics by a new team of scientists and a DNA "sweep" of staff at the intelligence service.
Asked if MI6 had agreed to the new measures, Hogan Howe replied: "They don't have to sign up to it - it's the law".
Until now the team probing the discovery of Mr Williams' body in a padlocked bag have had to go through colleagues in the counter terrorist command.
That unit has now been removed from the investigation and its failure to properly search and seize items from Mr Williams' office internally investigated.
The Yard believe a deeper and wider inquiry is needed given the family's suspicions Mr Williams' death was linked to his work.
A new detective will be placed in charge too following the promotion of Det Chief Insp Jackie Sebire who was thanked by the coroner and family for her efforts.