Incidentally, to be more accurate, the concorde crash to which you refer was caused by a fuel tank explosion. The source of ignition was caused by the tyre explosion, which may have been caused by a piece of metal on the runway. Either way Concorde did not have fuel tank protection, just like the Nimrod.
Sorry Nige you've got that wrong. Concorde had a ruptured fuel tank, caused by a burst tyre, other damage to the undercarriage also occurred. I believe the igntion source was not conclusively proved, but was thought to be arcing from damaged wiring in the undercarriage bay. The aircraft did not explode before hitting the ground. The crew could not maintain altitude and airspeed given the state of the aircraft and the engines.
S_H