A bottle-nosed whale was spotted in the Thames on Friday morning. The mammal got as far upstream as Chelsea.
"I saw it blow, it was a spout of water which sparkled in the air," said Tom Howard-Vyne, head of communications at the London Eye.
The RNLI sent a lifeboat to monitor the whale. Port of London Authority and London Fire Brigade vessels have also been in attendance.
The BBC and Sky News have helicopters overhead broadcasting live pictures.
Just over a year ago porpoises were spotted from Albert Embankment.
A PR firm based in Millbank Tower has set up a blog to track the whale's progress.
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