OK, here we go again....
I am given to understand that CART now have a Trolley Hotline Tel 01923 201120.
Shop-A-Trolley allows members of the public to report sightings of abandoned trolleys in CART's’ canals and rivers. This information will be used to help recover trolleys, to map hotspot areas and to identify a league table of the nation’s least and most environmentally responsible retailers.
So CART must think that the supermarkets themselves are throwing their own trolleys in the cut. Or as Jim Royal would say "environmentally responsible my bum"
Stray Shopping Carts: A Guide to Field Identification. The author is Julian Montague.
This book will be treasured by most boaters operating on the canals and rivers of the UK. It will help with species identification of those shopping trolleys to be found gracing the canals, rivers, towpath and other CART waterside habitats.