Another slot busting trick I heard applied at LGW many moons ago in the days of horrendous delays was when a crew inbound to LGW and aware of delays for their next departure, called for start on Box 2 while inbound on the ILS, to get a place in the queue. It backfired when ATC said they were in luck, somebody else had missed their slot and they could start immediately! Much embarrassed muttering into microphones.