A new mural unveiled by street artist Banksy has been defaced in south-east London.The piece, which shows a rhino mounting a Nissan Micra with a traffic cone on its bonnet, was spray painted with a tag by a man wearing a black balaclava at around 19:45 BST. Stephanie Lester, a witness who spoke to BBC News, said the man had “walked away from a jeering crowd”.