Martin Hickman: This marks an explosive development in the scandal
Analysis
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The expansion of Operation Tuleta from a "scoping exercise" to a full-blown investigation will open a new and explosive instalment in the phone-hacking scandal.
For a start, detectives are likely to investigate more egregious news-gathering techniques than phone hacking: computer hacking, burglary and "blagging" personal data.
Some of the targets of these techniques had more to lose than their privacy. While vile and disgusting, the alleged eavesdropping of Milly Dowler, war widows and Sara Payne did not endanger life and limb. The alleged targeting of ex-intelligence officers with knowledge of IRA informers could have.
Tuleta may also draw other titles and newspaper groups into the scandal. It is likely to focus on the activities of Jonathan Rees, a private detective who worked for News International and the Mirror Group. While police investigated Mr Rees over the murder of his business partner Danny Morgan in 1987, they bugged his office and recorded his conversations with reporters.
Mr Rees was acquitted of murder in March, but soon after fresh claims were made about his work for newspapers. Several of his reported victims such as Jack Straw and Peter Mandelson asked police if they had been targeted. That pressure may have persuaded Scotland Yard that the best way to end this scandal once and for all is to investigate all the "dark arts", not just phone hacking.