How do I clean my vintage eiderdown?

I have bought many vintage eiderdowns and although sometimes they look surprisingly clean, quite often I do like to know they've been freshly laundered before I use them. A while ago I enquired at my local dry cleaners where they charge about £12 but do not guarantee your eiderdown will remain intact or an even distribution of feathers. That seemed to me a complete waste of money so I always do it myself. Ensure any holes or tears are stitched and test the fabric for strength. The fabric from an original 30s or 40s quilt can be very fragile and I did once end up with a washer full of feathers. I usually clean two at a time in a large launderette washing machine before taking them home and drying as quickly as possible by hanging in the sun and more usually (thanks to the great british weather) airing above an electric heater/radiator. Tumble drying is usually recommended but I continually move and de-clump the feathers whilst drying and find this a good method. A quick tumble at the end will minimise creasing. Quite often old stains and water marks do not disappear completely but don't be too disappointed - they are usually lost in the pretty patterns and at least you know the eiderdown is clean when you put it on your bed.