What is British Rail Classes 251 and 261?
{{Infobox train | background = #2B5994 | name = ''Blue Pullman'' | image = Blue pullman 60099 - swansea - aug 1967.jpg | imagealt = | caption = Blue Pullman at [[Swansea railway station|Swansea station]] in 1967 | interiorimage = Interior of Pullman Motor Parlour Second (MPSL) W60646 (8322321847).jpg | interiorimagealt = | interiorcaption = Interior of Blue Pullman | service = 1960–1973 | manufacturer = [[Metro-Cammell|Metropolitan-Cammell]] | factory = | family = [[Pullman train (UK)|Blue Pullman]] | replaced = Steam locomotives and carriages | yearconstruction = 1959–1960 | yearservice = 12 September 1960 | refurbishment = 1969 | yearscrapped = 1974–1975 | numberconstruction = | numberbuilt = 5 sets (2 × 6-car; 3 × 8-car) | numberservice = | numberpreserved = | numberscrapped = All | successor = Separate locomotives and [[British Railways Mark 2|Mark 2]] coaches | formation = 6 or 8 cars per set | fleetnumbers = {{plainlist| *DMBFL: M60090–3 *DMBS: W60094–9 *MSL: W60644–9 *MFLRK: M60730–3 *TFLRK: W60734–9 *TFL: 60740–9 }} | capacity = ''6-car sets:'' 132<br>''8-car sets:'' 218 | operator = [[British Rail]] | depots = {{ubl|[[Old Oak Common TMD|Old Oak Common]]|[[Reading TMD|Reading]]|[[Tyseley TMD|Tyseley]]{{citation needed|date=October 2019}}}} | lines = ''6-car sets:'' [[London Midland Region of British Railways|London Midland Region]] (1960-1967) and [[Western Region of British Railways|Western Region]] (1967-1973)<br>''8-car sets:'' Western Region | carbody = [[Steel]]<br>Semi-integral | trainlength = {{convert|395|ft|m|2|abbr=on}} (MR)<br>{{convert|545|ft|1|in|m|2|abbr=on}} (WR) | carlength = {{convert|66|ft|5.5|in|m|2|abbr=on}} (power cars)<br>{{convert|65|ft|6|in|m|2|abbr=on}} (intermediate vehicles) | width = {{convert|9|ft|6|in|m|2|abbr=on}} | height = {{convert|12|ft|4.5|in|m|2|abbr=on}} | floorheight = | platformheight = | entrylevelorstep = | doors = Hinged slam, centrally locked | art-sections = | maxspeed = {{convert|90|mph|km/h|0|abbr=on}} | weight = ''6-car sets:'' {{convert|299|LT|ST