Newcastle University's Conor O'Neill, who carried out research into the effects of a bomb blast inside a train carriage, said using special materials could prevent shrapnel injuring passengers.
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The Met Police says 143 firearms have been handed in at stations across the capital in just seven days, including two antique machine guns.
The pair filmed themselves clinging on as the train travelled from Essex to London at high speed.
Around 60 firefighters tackled the blaze at the four-storey building in Daleham Gardens, Hampstead, that broke out early on Tuesday.