Mayor of London Boris Johnson has opened a new technology centre this morning near the Barbican.
The Digital Media Development Centre is run by the website Amazon and will bring 100 jobs to the capital.
The mayor is hoping it will boost London's reputation as a high-tech city.
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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.