Frang,
With due respect for an otherwise impeccable post, the stuff that went through the wing at Dulles in 79 was metal. The wheel broke up following a tyreburst. It was after that that the regulators required Concorde's wheels to be built so they could run safely with no tyre all the way to rotate.
When the CAA eventually grounded the BA fleet after Gonesse, it was because they had, by then, established the size and weight of the piece of rubber that caused the Gonesse accident. All tyreburst tests done before this had shown that pieces of rubber/carcass would be 1kg or less (I think that was the weight), and ballistic tests had demonstrated that the aircraft could survive the damage that chunks of that size would cause. When they found that the chunk of tyre at CdG was much larger and heavier, theoretically because the tyre had been cut in the way the BEA said it was, they had to admit that, without further protection, the argument that Concorde's design was still safe had just been destroyed by an unexpected set of circumstances.