Like it says "Ideas wanted for removing dried-on blood stains from linen". I tried a couple of days soaking in diluted Persil, then a 60C wash in the machine. Still there. The spots are quite small, around 1/4inch dia.
Then I tried an Oxalic Acid Dihydrate solution which had no effect.
While I'm here, my daughter has red wine stains on her wedding dress which cleaner shops tell her is impossible to remove. Presumably they mean without bleaching out the dress colour.