Greater Manchester Police Assistant Chief Constable Garry Shewan has revealed details of an arrest made over an offensive Facebook page created after the deaths of PC Fiona Bone and PC Nicola Hughes.
Speaking at news conference, he said an investigation by Greater Manchester Police and Merseyside Police led to the arrest of a 22-year-old man from Merseyside last night.
He remains in custody and is being questioned.
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Detectives in Westminster are investigating after the man was discovered on the Route 189 bus in Marylebone shortly after midnight.
The murderer was shaking and appeared to be gasping for air for around 13 minutes before dying.
The positive results come after Chancellor Philip Hammond admitted the government is prepared to sell its stake at a loss to the taxpayer.