This was one of those locomotives which, for no reason apparent at this distance, was rebuilt time and again for a very long life. This is the  first GWR No 40, which was officially withdrawn in 1904! It was constructed as a long boilered 0-4-2 tender engine with outside cylinders in 1849 by R.B. Longridge & Co of Bedlington, for the Shrewsbury and Birmingham Railway, and was so well regarded that the S&B attempted to sell it without success. In 1854 it became GWR property. In 1858 Armstrong had it completely reconstructed as an 0-4-2ST with inside cylinders, possibly using the old boiler, much modified, but little else. In 1873 it was reconstructed again, still as an 0-4-2ST, but with new cylinders and boiler. Finally in 1897 it received new boiler and cylinders again. Ahrons has a neat phrase for these complete rebuilds come renewals: "Reusing the space between the wheels" and in this case it seems entirely appropriate.

 I wonder how Armstrong saw all these locomotives. Did he treat them as classes, or as individuals, upgraded/rebuilt or withdrawn according to their merits and the state of the GWR bank balance? Presumably when one of these antiques and curios came into the factory some long vanished notebook contained estimates of what was going to be needed to repair it to run until another overhaul was due, and George Armstrong would look at what it was going to cost and where there was capacity in the factory, and a decision on high would be promulgated to scrap or rebuild. Its also worth considering, I think, too, that we need to consider that because so much had been replaced over the years, in 1897 it was not so much a question of putting a new boiler and cylinders on an 1849 locomotive, but rebuilding an 1873 one. Maybe too the Chester workshops, which had once been the works of the Shrewsbury and Cheseter, was adept at keeping the old crocks running. Its striking just how many of the oddities survived in that area, and how few were in front of Dean or Churchward's eyes at Swindon!