‘No sharks but I’ve seen porpoises’: the rebirth of the River Thames

A trip down London's famous waterway reveals many signs of life - but is this another false dawn?

The Thames shark hunt begins on a swirling golden brown river, where high above Battersea power station soars a speck that may be another awesome predator: a peregrine falcon.

I haven't seen a shark but I've seen porpoises up the Thames and there were a couple of whales last year," says Alfie Gardner, captain of one of the Thames Clipper Uber Boats that whisk commuters and tourists up and downriver. We see a lot of seals. Near enough every day."