I've tried everywhere on the net but can't seem to find any information on cleaning lead.
I have a substantial amount of decorative lead flashing on two front bay windows that are heavily marked with mortar splashes etc. Can anybody tell me the best way to clean it. I heard something about some kind of special oil for cleaning lead but no more info than that - any advice would be much appreciated.

MrC writes:

I have a substantial amount of decorative lead flashing on two front
bay windows that are heavily marked with mortar splashes etc. Can
anybody tell me the best way to clean it.

Acid. CLR is a suitable retail product.