I agree. I cannot find any record of this registration either. My fellow pilot also records WL540 in his logbook. The flight was at RNAS Yeovilton on 6th Dec '74 and neither of us can remember whose a/c it was. (senile dementia is not a factor) We were visiting 892 NAS pilots on detachment. It could have been Station Flight, or attached to NFSF, or even visiting from Church Fenton.
Anyone got any ideas?