Timothy Murphy wrote:
I have inherited a rather nice letter box.
However, the flap does not close properly
because the spring which is meant to hold it closed
is broken.

This is a small helical or cylindrical spring on a small rod.
I've looked around at a few hardware stores,
but not seen any such springs on offer.
Is it possible to purchase them on-line somewhere?

Or is there some other way of stopping wind
blowing through the letter box?

Possibly buy a cheap letter-plate with a similar design of spring - and
transfer the spring over to the inherited one.

Cash