The FDC's have been made in the 'old' way, because that is the way I was educated and the way I know. This is also the way they would have been made in the 1950's, and are of necessity the way they have to be done to prove my above point. They would have been acceptable in-toto at that time, which was before the present over-regulated and litigious environment appeared, and would have built seamlessly onto existing steam loco design practice. If, therefore, the steam fraternity had not been so short sighted at the time of nationalisation of the railways in the UK in 1948, and a small amount of money had been set aside for a true steam development section, charged with producing designs for the future at the same time as the BR Standards were being produced for the then-present, something like the 5AT could have appeared by the mid 1950's when the BR Standards were already becoming obsolete, and could have taken over from them in a continuous seamless development of steam traction technology. If it had been done in this way and steam had continued to develop, then its technology would have developed naturally to satisfy today's standards. But it has not been so, and the gap which exists between the way things were done in steam times and today's requirements is a major problem. Thus some of the FDC's that would have been quite acceptable in steam times are not now. For example FDC.16. "Stability" is probably in advance of whatever was done then (which would have been mostly based on empiricism and experience) but will not satisfy today's requirements, which require a computer simulation to be developed just for a 4-6-0. This limitation is freely acknowledged, and in such cases whatever has been done provides no more than a base from which a theory acceptable by today's standards must be developed by those who are knowledgeable enough to do it.