Stuart Noble wrote:
The rings should change colour naturally if left uncovered. The only
bleach worth talking about is the 2 part peroxide stuff, which isn't
cheap, and may well reduce the life of the wood. Oxalic acid is
recommended for decking but it seems like a lot of money for what it is.
I've never had much luck with it

Thanks, Stuart. Have googled a bit and found warnings against using
chlorine bleach, but that oxygen bleach is the thing to use, followed by
several coats of "synthetic epoxy resin water repellent". Will have to
have a look round BnQ and/or Focus to see if these products are
available. This could be good, the only problem in my case is that the
previous owner threw salt around when it snowed and all the screws have
turned rusty and the rust has impregnated the immediately-surrounding
wood. I doubt if the oxygen bleach will remove this as well. Instead
it seems to me it will show these rust circles up.

My previous thought was to use an ebony wood preservative, as black
hides a multitude of sins, but various sites suggest that the film/paint
is no end of trouble.

What to do?

Eddy.