London City is (obviously) a licenced airfield. At weekends they close from 1230 Saturday to 1230 Sunday, and at that time it is unlicenced it would appear.
Once a year they have their "Fun day" on the Saturday afternoon, with light aircraft in, aerobatics, etc. Yet though the guys are up in the tower and all is above board they revert to A/G radio only and always are precise to correct anybody coming in (PPR of course) who calls them by their normal callsigns. Makes me wonder what happens and whether they go unlicenced for the afternoon for some reason.