The fourth and fifth digits usually represent the locomotive's BR number, with a few exceptions. Some ex-LNER locomotives have numbers based on their LNER pre-1946 numbers, these being Class A3 "Flying Scotsman" (4472), Class A4s "Mallard" (4468) and "Sir Nigel Gresley" (4498), LNER Class J36 "Maude" (NBR 673, LNER pre-1946 9673) and Class V2 "Green Arrow" (4771). Furthermore, the aforementioned locomotives not of BR origin obviously cannot have numbers based on non-existent BR numbers, so "Lady Armaghdale" number is based on the works number 686, "Barbara" on the works number of its 1962 rebuild, and "Tornado" is assigned the number it carries, 60163, being one greater than the last of the previous Peppercorn A1s.