The Queen will visit Lords cricket ground today ahead of the second Ashes Test between England and Australia.
The monarch will be presented to the players before play gets underway at 11.15am.
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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.