For the friction tests at Cranfield, long shallow rubber tanks were installed on the runway and these were filled with water for the trials. The main wheels were marked so that high speed cameras could show wheel movement as they passed through the water. I left Cranfield in late 1966 and the Swift was replaced by a Hunter just before that. The test pilot seemed to shed twenty years when he stopped flying the Swift although that may have had more to do with the arrival at Cranfield of some of the aircraft from filming of "The Magnificent Men..." . I think he spent more time flying those than he did the Hunter.