Ah, my first ever MTB was a 23.5" Dawes Wildcat. He'll grow into it the old chap in the shop said. Maybe if I was still growing now it would be about right. I owe the few bike handling skills I have now to that bike. If I slipped forwards it was all over! Can I ride that section? If the alternative is slapping your plums violently onto a metal bar, then, yes I can ride that section.
Back then, MTBs seemed to come in three sizes. 19.5" was the smallest size Dawes offered! How I wished I had got one of those! He would need to be very tall!