Okay I'm a few days late, but Motoring George Spauwen, a Dutch Vintage Motorcycle Association member (and prewar Triumph twin fanatic), sent a timely note reminding me that on October 8, 1938, Ivan Wicksteed used his supercharged Triumph Speed Twin to take the Brooklands Outer Circuit lap record at 118.02mph. That's really going some for the early six-stud Triumph engine, and I know there were troubles encountered with 'total cylinder filling', mainly with the barrels pulling completely off the crankcases due to the inadequate clamping of six little studs. The barrels were soon changed to an 8-stud design, which stood Triumph twins in good stead for decades.
Wicksteed began racing at Brooklands in 1934, using a 350cc Cotton-Blackburne, but was disappointed that he could only reach 76.61mph on the flying kilo; not enough for an ambitious speedman. He sold the Cotton and bought a Rudge, replacing its engine with a JAP racing ohv. By 1936, he had moved up to a 500cc Excelsior, and gained his Gold Star with a lap of 101.64mph. He also sprinted an Excelsior 'Mechanical Marvel' 250cc ohc at the likes of Gatwick.
In 1937, he switched to racing Triumphs, using a single cylinder 500cc machine to raise the fastest 500cc lap to 110.68mph. Later in the year, he acquired a new Speed Twin, which (as mentioned) gave lots of trouble during its development, but Wicksteed carried on and was eventually able to reliably lap Brooklands at 107mph. I note also that Wicksteed competed for the 'Professor A. M. Low Cup' all-comers 3-lap handicap race in '37 (see more about Low in a previous post).
In 1938, he modified his Speed Twin to accept an Arnott supercharger, which brought yet more problems, not only with mechanical reliability, but the handling of the machine seemed to worsen as the speed increased! [It has long been said that Edward Turner, designer of the Triumph Speed Twin, chose his steering head angle for aesthetic appeal, as a more stable but longer steering angle left too much space between the front mudguard and the frame!]
Eventually the blown Triumph had a claimed capability of lapping the course at 122mph, with a top speed of 127mph, and Ivan decided to make his attempt at the 500cc lap record. On October 8, 1938, conditions were poor, with rain and a strong southwesterly wind, but the Hutchinson 100 race was likely the last possible venue for his speed record of that year (Brooklands records were generally recorded during a race, unless a long-distance speed attempt was undertaken). He was successful in taking the 500cc lap record at 118.02mph, which brought Mr. Wicksteed immortality, as the record still stands. The track was closed in 1939 for war preparations (with important Vickers avaiation facilities integrated into the circuit), and was too badly damaged during WW2 to reopen postwar.
A reproduction of Wicksteed's machine can be seen in the Brooklands Museum (color photos).
Other photos and information taken from 'All the Years at Brooklands' (Bayley) and 'A Clubman at Brooklands' (Perryman).