Adrian Walls from London Zoo explains why keepers have installed a diving board in the penguin enclosure in the run-up to the 2012 Olympics.
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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.