If you saw Martin Parr and didn't know who he was, you would barely notice him. He is Mr Invisible and Mr Normal rolled into one, in his sensible jumper probably from Marks & Spencer and sensible socks and sandals. He has a neat side parting and neatly cut hair. He has a mild and conventional manner and a mild and conventional appearance. There is something of the naff birdwatcher about him. But do not be fooled.