It is widely expected that Home Secretary Theresa May will make an announcement on an independent judge-led inquiry into the murder of Daniel Morgan.
The private investigator was found with an axe in his head in a London pub car park in 1987.
It has been claimed that police corruption prevented the murder from being solved despite six criminal investigations.
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A 35-year-old and a 27-year-old man, both from the Birmingham area, have been arrested and remain in police custody.
Molly Owens, was reported missing on Friday and is believed to be with her father, who is wanted after failing to appear in court.
Former Diversity dancer Robert Anker has died in a car crash in Canada.