FYI my understanding is that, in London at least, cabs aren't allowed to operated with a broken card reader; if that happens to you, tell them that you have no

FYI my understanding is that, in London at least, cabs aren't allowed to operated with a broken card reader; if that happens to you, tell them that you have no cash and either it will suddenly magically work or you'll get a free ride (this has happened to me).