Police hunting for Michael Cope over the murder of his ex-girlfriend Linzi Ashton urged him to give himself up.
Superintendent Kevin Mulligan warned: "If anyone is harbouring this individual, they will be prosecuted."
He added that Cope had a "history of violent behaviour".
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The operation to recover the unexploded bomb near the Houses of Parliament let to disruption in central London overnight.
Southern parts of England and Wales will see sunny skies after a frosty start.
A police spokesman said the incident in the Bourke Street Mall on Friday was not related to terrorism.