Blue-Green Algae in Hampstead Swimming Ponds - Dangerous or Safe to Swim?

There has been talk of algae appearing in the Hampstead Heath swimming ponds lately. Signs have appeared at the men's swimming pond.

    According to the sign, the s*** of the algae can cause stomach upsets and more serious health issues. The advice on the sign suggests that avoiding the s***, and the water around it, especially if you have children or animals, is a good idea.

    Yet there doesn't seem to be many people paying attention to the sign. Swimmers are still using the pond, and many have told the Ham&High that they will continue using the ponds despite the advice.

    So seeing as people are ignoring the signs, and there have been no reports so far of people becoming ill from swimming, are the signs just the powers-that-be erring on the side of caution? Should we be concerned, or, quite simply, just get on with it?