 GNER also began to have their InterCity 125 sets a further refit to bring them to the same "Mallard" standard as their recently refurbished InterCity 225 fleet, a programme that has been continued by National Express.The Great Western power cars have had major modifications to their cooling system to prevent overheating on hot days.GNER's solution to the overheating problem was to haul sets under the wires using Class 91 electric Locomotives.