Radarspod - if an a/c is fully ready for departure then I imagine that the SSR interrogation will have been turned on as part of the departure checks (doubt very much it happens just after rotation). Unfortunately LHR has a couple of taxiways that are high enough for a/c to give a good signal to the Swanwick radars and occasionally (although not regular) are caught. For those that don't know this activates the flight in the centre computer and produces times and details to the radar controllers which are wrong as its a false activation. I would say personally last year this happenned 4 times, normally a heavy jet taxiing out of Terminal 4. So squalking IDENT could affect the Swanwick system.