sir herbert nigel gresley (19 june 1876 – 5 april 1941) was a british railway engineer. he was one of britain's most famous steam locomotive engineers, who rose to become chief mechanical engineer (cme) of the london and north eastern railway (lner). he was the designer of some of the most famous steam locomotives in britain, including the lner class a1 and lner class a4 4-6-2 pacific engines. an a1 pacific, "flying scotsman", was the first steam locomotive officially recorded over 100 mph in passenger service, and an a4, number 4468 "mallard", still holds the record for being the fastest steam locomotive in the world (126 mph).