What's this, then? It's the all-new, fourth-generation Mazda MX-5, or Mazda MX-5 'Miata', if you're an American. And by all-new, you mean ‘a bit different to the old one'? No, all-new. Fresh from the ground up, and both lighter and smaller than the car it replaces. The MX-5 has lost 10 per cent of its body weight, over 100kg, and is now even shorter than the 1989 original. That's virtually unheard