A Metropolitan police spokesman said officers had completed their searches of all four properties today and no hazardous materials had been found.
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Singer Adele and Hollywood star Jennifer Lawrence were among the protesters on the anniversary of the US president's inauguration.
The proposals are being introduced in order to help create more equality in the treatment of physical and mental health.
The prime minister said "tough new rules" will be introduced to tackle the behaviour of executives who put their workers' pensions at risk.