First powered solo ( I already had about 40 hours gliding in my log book) was at Cambridge in C150s. One November afternoon, I was on my 3rd or 4th trip of the day so I lined up, advanced the throttle and as we gathered speed eased it off the ground.
My instructor immediately said 'pity it's just about to get dark otherwise after that takeoff, I'd send you solo now; never mind we'll do it first thing tomorrow'.
And we did! None of this 'instructor jumping out with no warning and saying fly one circuit' etc, I knew in advance!