I had better revise post#11 as a head count has just revealed a record 700 grey seals in the estuary and they are spotted well upstream now even swimming beyond Tower Bridge.
A PS:
http://news.bbcimg.co.uk/media/image...0820-00010.jpg
Last week's female dolphin seen 20 miles upstream at Chester on the River Dee.
Spectators amused by "playful" daily leaps but more likely to be distressed and trying to make sense of its surroundings. Rescue charity has captured her now and safely returned to deep water.