The controller denied him start, and told him that he had to re-file (for another massive delay). The aircraft in question just couldn't believe it - and assured the controller he could be at the holding point in 8 minutes or so and that he would be reporting him.
HunderPercent, be aware that there is a number of pilots everyday, that are just lying in order to fool the ATC that they can make the slot while they know they can't. I'm an ATCo who does his best to get you airborne, sometimes even slightly outside your CTOT window. But yesterday a crew asked for startup precisely at CTOT (relatively small aerodrome, pushback+taxi time is 10min). I asked if they can make it. Yes, they do. OK, so startup approved, expedite due slot. Well, the aircraft was pushed back ten minutes later (so the slot window was just about to end), whereas it takes usually 2-3min. OK, I thought, maybe there was some unexpected problem, hell, gave them clearance to taxi. Wow, a slow grass-cutting tractor going the same direction had overtaken them with twice their speed! No mention that there were several aircraft taxiing behind. No apparent reaction to expedite request, so finally they arrived at the holding point 12min after CTOT window. And yes, I did clear them for takeoff, because I think that aircraft with engines running should get airborne. But I broke all the rules this way. I don't like this, because my duty is to obey them, that's what I get paid for. So it's you (or some of you) who ruin the trust. For the next few shifts I will be very suspicious of crews declaring that they 'can make it'. And maybe next time I will return somebody to the gate.
BTW, there are (huge and well-known) airlines, that apparently don't experience this problems while operating in the very same environment. They always make the slot and if not, they don't discuss and get themselves a delay to EOBT and accept the new slot. German precision?