This question is asked of bus drivers between 9.15 and 9.29 am. You have to be over 60 to ask it because you need the relevant bus pass. At 9.30 it is legally valid. At 9.29 the driver will probably let you on. At 9.20 you are pushing your luck but it may be worth a try.
I use the buses a lot. On Wednesday morning I arrived at a stop at 9.21. Four of us sat on the bench. I must have been easily the youngest.
At 9.22 a bus came and the other three popped the question, only to be told that they were indeed 'twirly'. By the time the next bus came and let us on, I had got to know them.