Olympic bronze medallist Alex Partridge tweeted to say:
Please everyone the medals still have not been found. Please keep your eyes open all around London.Thank you again for your amazing support.
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Mr Blavatnik, whose empire includes the Warner Music Group, has an estimated fortune of £13.17bn according to the Sunday Times Rich List.
Find out what to expect from the weather if you are running in the big race in London or watching from the sidelines.
It will be a soggy start to the weekend and temperatures will drop making it feel colder than in recent days.