I found out that all bicycles with gears have a single Aquilles heel. The rear mech hanger of my Ridgeback Meteor has a crack. It is unsafe to ride the bike. The piece is made of aluminium.
The store where I bought the bike in London (Evanscycle) cannot locate its reference. Ridgeback does not does not provide the information online nor answer to emails enquiring about the hanger.
I ordered a gear mech derailler hanger on ebay to a French merchant, Alpine Bikers. They do not answer to questions on ebay but they do ship spares made of aluminium.
If you think of the hanger as having the shape of a seahorse, the replacement piece has a mouth a bit too long. It cannot be attached to the frame for that reason. My local key-maker trimmed some 2 mm off the piece and the trick work: my bike is on the road again.
This is the result and how it fitted back in its place.
There are protectors of derailleurs available that are worth considering for all-terrain bicycles. It you attach one protector to your bike, leave one of its two holes without screw; this way it still protects the derailleur from direct lateral impacts but it would break or twist where one of the screws is missing thus preventing further damage to the frame, which would be fatal to the bicicycle.