Jimmy... "after take off" is correct in one sense...
At Heathrow we tried a number of stupid procedures. One involved telling the pilots something like "90 seconds after rolling contact xxx". This was to reduce their workload during the take-off period. Unfortunately, one pilot missed the "90 seconds after rolling" bit and called London Control before entering the runway. The radar man went back with his usual phrase: "Climb to 6000 ft..." so the pilot interpreted that as a clearance from where he was to 6000 ft..... so without another word he entered the runway and took off, much to the amazement of the Heathrow Tower controller!!
There's always one...........