Firstly you cannot have a 1962 Fordson Major Diesel as the FMD was not built after 1958. If the tractor is indeed 1962 it is a Super Major and these had a different brake system. The brakes on both tractors are on the bull pinion shafts, FMD brakes are shoe brakes operated by cables and are mounted on the end of the bull pinion shafts just behind the mud wings on the level of the footplates. The drums are behind a tin cover held on by three screws and are adjusted through the drum.
The Super Major has disc brakes mounted on the bull pinion shafts close to the axles housing, (you are possibly resting your feet on them) ;0) Look under the footplate and you will see a linkage from the pedal to the front of the brake housing. In the centre of this linkage, where it enters the brake housing, is a Nylok nut. Turn this nut anticlockwise to slacken off the brake. Then try driving backwards. The brake should free off possibly with a bit of a "Bang".
Super Major brakes are known for sticking when they need cleaning out but can be freed by driving in reverse when they stick on. The answer is to strip the brakes and clean the rust from the splined shaft and the actuating plates. Not a bad job.