Deputy Assistant Commissioner Martin Hewitt, of the Metropolitan Police, says there remains "gaps in understanding" regarding the death of MI6 worker Gareth Williams.
But he has concluded, following two years of investigation, that it is "most probable" that the codebreaker was alone at the time of his death.
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Pair charged after woman was found being held in conditions of 'domestic servitude' in the Manchester area, police said.
The men were held over a stash of thousands of gun cartridges and more than 20 pistols and rifles, coastguards said.
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