The A4 pacifics were designed for low consumption of coal and water on all kinds of services; passenger and freight. With the introduction of the double-exhaust Kylchap[?] funnel[?], the consumption levels of the above dropped even more, gaining more revenue to their operators.
On July 3, 1938 the Mallard with the newly modified funnel to Kylchap, set a world speed record of 125 mph, pulling six cars plus a dynamometer[?] car. Although the dynamometer car indicated a top speed of 126 mph, Sir Nigel Gresley never accepted this speed as the record-breaking maximum. He claimed this speed could only have been attained over a few yards. He was comfortable that the German speed record of 124.5 mph had been surpassed.
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