Preheat the oven to 200C/400F/Gas 6 (180C fan)
Peel and chop the onion then heat the oil in a small roasting pan and cook the onion for 5-10 minutes until beginning to soften. Remove from the heat and spoon some of the onion into the cavity of the birds along with a sprig of thyme each and a knob of butter. then scoop the rest into the centre of the tin.
Wrap the birds in the Carmarthen Ham then season with pepper and lay on top of the onions. Pour over half the cider and roast for 15 minutes then reduce the oven to 180C/375F/Gas 5 (160C fan), cover the birds with foil and cook for a further 10 minutes. Remove from the oven and lift the birds onto a warm plate to rest.
Pour away any excess fat and put the tin over a medium heat. Add the remaining cider and scrape the bottom of the tin to release the caramelised juices. Boil until reduced by half then stir in the apple cinnamon curd and season to taste. Sieve into a warm jug.
Place the whole partridge onto each warm dinner plate and serve with the cider jus, seasonal vegetables and roast potatoes.