All leave has been cancelled for the gun-carrying officers in the capital in the largest ever mobilisation by Scotland Yard which will see 6,000 police officers deployed on the streets.
The Telegraph reports the move comes following an intelligence warning that Islamists may be planning a high profile attack on a European city, although there is no evidence to suggest London is being specifically targeted.
The warning comes following the terrorist attack in Paris in November which 130 people killed in the city by roving gunmen.
