BR Mk1 BSO ADB977135HOR R40348 Hornby BR, Mk1 BSO, ADB977135 Era 8 2022 Catalogue British Railways Mark 1 is the family designation for the first standardised designs of railway carriages built by British Railways (BR) from 1951 until 1974, now used only for charter services on the main lines or on preserved railways. Following nationalisation in 1948, BR had continued to build carriages to the designs of the "Big Four" companies (the Great Western, Southern, London