Original: Part of the TGV family, it has a smaller cross-section to fit within the constrictive British loading gauge, was originally able to operate on the UK third rail network, and has extensive fireproofing in case of fire in the tunnel.
Simplified: Part of the TGV family, it has a smaller cross-section to fit within the constrictive British loading gauge, was originally able to operate on the UK third rail network, and has a lot of fireproofing in case of fire in the tunnel.