Loughborough MP Nicky Morgan says she "heard an almighty bang" and "saw clouds of thick black smoke" as the helicopter crashed into a crane in South London this morning.
The MP was walking towards Vauxhall tube station, when the accident happened.
"Ms Morgan says she "saw clouds and clouds of thick black smoke billowing from the ground" and that initial thoughts were that a bomb had exploded."
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His victim, who was bed ridden, died four weeks later.
Police say that although the robbers made off with cash, nobody was injured in the siege.
Dry with sunny periods, although cloudier in south this morning.