and accelerated downhill. The speeds at the end of each mile (1.6 km) from the summit were recorded as: 87, 96, 104, 107, 111, 116 and 119 mph (141, 155, 167, 172, 179, 187 and 192 km/h); half-mile (800 m) readings after that gave 120, 122, 123, 124 and finally 125 mph (194, 197, 198, 200 and 201 km/h). However, the dynamometer car tracks the current speed every half second on a paper roll moving 24 inches for every mile travelled. Speeds could be calculated by measuring the distance between the timing marks. Immediately after the run staff in the dynamometer car calculated the speed over five second intervals, finding a maximum of 125 mph. Although 126 mph was seen for a single second, Gresley would not accept this as a reliable measurement and 125 miles an hour was the figure published. Gresley planned to have another attempt in September 1939, but this was prevented by the outbreak of World War II. In 1948, plaques proposed and designed by Harry Underwood, a headmaster and keen steam enthusiast, were fixed onto the locomotive which stated 126 miles an hour, and this became the generally accepted speed. Despite this, some writers have commented on the implausibility of the rapid changes in speed. A recent analysis has claimed that the paper roll was not moving at a constant rate, and the peaks and troughs in the speed curve resulting in claims of 125 mph held for 5 seconds and 126 mph for one second were just a result of this measuring inaccuracy. It concluded that a verifiable maximum speed being a sustained 124 mph (199.36 km/h) for almost a mile. On 3 July 2013, the 75th anniversary of the speed record, all six surviving A4 locomotives were brought together at the National Railway Museum. Rival claims Mallards record has never been officially exceeded by a steam locomotive, although a German DRG Class 05 reached 124 mph in 1936 on a horizontal stretch of track, unlike Stoke Bank, which is slightly downhill. However, the Class 05 hauled a four-coach train of 197 tons, whereas Mallards seven-coach train weighed 240 tons. There are claims that the Milwaukee Road class F7 and PRR S1 locomotives attained service speeds faster than Mallard, and although fines from the ICC claim that the PRR S1 reached 153 mph, Mallard's record remains. The LNER A4 and PRR T1 classes had