How are you supposed to recognise a dog type that is dangerous / banned?
http://en.wikipedia.org/wiki/Dangerous_Dogs_Act_1991
Pit Bull Terrier, Japanese Tosa, Dogo Argentino, Fila Brasileiro
These dog types look very similar to many other dogs that are not banned.
You can't recognise it easily. Even those with training in breed identification often struggle to pick out the breeds of mixed dogs.
You can, however, do a DNA test - something that the RSPCA are considering on some dogs in their care.