Q. I have old Edwardian cast iron gutters and down pipes that are quite rusty but otherwise intact, is there any way I can protect them from further deterioration? 

A. Yes, remove all debris and clean them as best you can. A power washer would be ideal to shift the old ground in dirt. If you don’t own a power washer, you can rent one in your local hire shop for a few quid a day. After the gutters have dried fully, get your hands on some that old ever-useful Owatrol oil and a can of exterior quality oil based gloss paint, whichever color you choose. Mix them up half owatrol and half paint, and apply directly to the rusted gutters with an appropriate paintbrush. For your information this mixture will do two things at the same time, i.e. it will penetrate deeply into the rusty steel, getting into all the small nooks and crannies, pushing out any remaining moisture and air while giving it color at the same time. This idea also makes a solid color oil based stain that works great on wood, concrete etc.