Two people, including a 19-year-old girl, are in critical condition after a bus crashed into a tree in Kennington, a police sergeant at the scene has confirmed.
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Specialist explosive detection dogs searched through the town examining letter boxes and phone booths for signs of potential devices.
Temperatures soared to 27.9C in Northolt shortly after midday on Thursday, making it the warmest April day for 69 years.
The South East will enjoy the best of the weather and along with Paris will be the hottest place in Europe.