Rinse the chicken legs under water and place into a stockpot. Cover with wine and water, bring to the boil, then reduce heat to simmer. Melt oil in a large saucepan. Add potatoes, leek, garlic and capers. Cook for 5-6 minutes on a medium heat then add to chicken in stockpot. Add tomatoes and saffron and bring to the boil. Cook for 10-15 minutes, until potatoes are soft.
Remove chicken legs from the stockpot. Scrape off skin and discard. Work the meat of the bones and return to stockpot. Add thyme, olives and parsley, and season with salt and pepper.
Drizzle olive oil onto the soup and serve.