Halve the vanilla pod lengthways, scrape out the black seeds and put in a large saucepan with the wine, sugar, cinnamon and thyme. Cut each piece of pod into three long thin strips, add to pan, then lower in the pears.
Poach the pears, covered, for 20-30 mins, making sure they are covered in the wine. The cooking time will very much depend on the ripeness of your pears – they should be tender all the way through when pierced with a cocktail stick. You can make these up to 2 days ahead and chill.
Take the pears from the pan, then boil the liquid to reduce it by half so that it’s syrupy.