Readbacks
With conditional clearances being a useful tool for ATC. Pilots should be aware that controllers are looking for a correct readback verbatim to ensure its been properly understood. I think the UK have filed a difference with ICAO using the phrase "after". Hope this helps otherwise it should open up some more interesting debate !!!! AIC 11/95 gives some insight into runway incursions which I suppose are the result at times of misunderstanding a conditional clearance ?