Peter Reeve, the gunman who shot dead off-duty officer Pc Ian Dibell yesterday, has been found dead in a churchyard in Writtle, near Chelmsford.
The family of Pc Dibell called him a "hero" and said he had paid for his actions "in the most devastating way".
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The high of 35C was recorded on a Bakerloo line train between Piccadilly Circus and Oxford Circus at 2pm.
Weather forecasters say temperatures could reach 35C, beating the previous record of 34.6C in the scorching summer of 1976.
After years of political manoeuvring over the future expansion of Heathrow Airport, there has been an important development this lunchtime.