The service was suspended during World War 2, and it was not until 1954 that the 105-minute schedule was again achieved. During this time "The Bristolian" became one of the few named trains to be scheduled for haulage by a gas turbine locomotive when, between April and May 1952 it was scheduled for haulage by 18100, the Metropolitan-Vickers experimental locomotive; but otherwise the mid 1950s was a time of very fast running under steam haulage, the intention being to reduce the regular schedule below 100 minutes. The fastest recorded was hauled by 7018 "Drysllwyn Castle" in April 1958, taking 93 minutes 50 seconds with a top speed of 102 mph. The change to diesel traction saw "Warship" class D805 "Benbow" haul an 8-coach "Bristolian" on the opening day of the 1959 summer timetable in 93 minutes 48 seconds, and over that summer several similar times were recorded until civil engineering concerns placed a 90 mph limit on the line, and the 100 mph running required for such times was no longer possible.