More than 700 seals have been recorded in the Thames Estuary.
In the first ever count by air, land and sea, the Zoological Society of London found hundreds of grey and harbour seals along the Thames and in small creeks and rivers.
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George Michael died in December last year at the age of 53.
PC Keith Palmer, 48, stabbed by Khalid Masood while on duty in the grounds of the Palace of Westminster last Wednesday.
Those gathered on the bridge fell silent at 2.40pm - the time the first call was made to police exactly seven days ago.