If you lived in the Margetson road/ Wordsworth Avenue neighborhood of Parson Cross estate in the years 1950/53 you may remember or have seen this unfortunate lad.
He was about 16 or 17 years old back then and severely retarded with mogoloid features and teeth and gums that protruded outwards beyond his lips. I dont know what his real name was but all the kids called him Mad Johnny and he always wore a Britsh navy seaman's hat. He liked to chase kids on bikes, trying to catch hold of the backs of the saddles and yelling his head off.
To us youngsters he was pretty scary looking.
I heard later on whether true or false that he became a bit violent and they put him away.