The current Mk6 is of course not much more than a heavily facelifted Mk5. But the Mk7 is all-new, sitting on an entirely fresh and highly configurable VW Group platform called MQB. Model for model, new Golfs will be at least 70kg lighter than the ones they replace. Savings come from extra high-strength steel in the shell, optimised suspensions, and lighter engines and ancillaries. But there's more to it than that. Volkswagen has patented a special welding process that means it can build GTI bodyshells with aluminium roofs, mixed up along the production line with steel-roofed regular Golfs. This means the weight drop for the GTI will be about 100kg compared with now, because it will have aluminium welded into the shell as well as in bolt-ons like the bonnet.