found out wot the black box is on the fuel filler pipe,

this is an "evaporative emission control"

what it does is harbour the fuel fumes from the petrol tank,and sends them to the fuel system to be burnt with fuel,

it must be an early version of the modern norm fitted to todays cars

inside it is charcoal ,which stores the fumes till such time they are sucked out,

so if anyone has a smelly petrol wiff about their car,and theres no obvious signs of leaks,then it could be that either split or venting off.ie broke.

hope this informs and helps.(sad or wot!)