WB must have meant Woodbridge which along with Manston and Carnaby were built as emergency landing strips for damaged aircraft and also acted as Master Diversion Airfields with FIDO. Woodbridge had a 3000m hard surface with 500m grass undershoot/overshoot. This still is only a total of 4km or about half of what Winkle quotes in his autobio.
Anyone know of any longer runways at that time?