I first asked that question 26 years ago and never got an answer so when visitors arrived I used to slip a condom into the young fellas top pocket!
the pockets are used to hide their parents rock of crack cocaine?...
dope - a few Rizzlas - knuckle duster - condoms - few rusk crumbs which smell like vomitus - rolled up copy of the telegraph
... tit mag for the potty...