Preheat the oven to 200°C/gas mark 6. Soak the green lentils in cold water for one hour, then rinse and place into a pan. Cover with chicken stock and bring to the boil. Simmer for approximately 15 minutes. Add the finely diced celery and carrot just before the end of cooking and cook on for a further 10 minutes.
Take the partridges and place one bay leaf on the crown of each breast, then wrap the remaining rashers of bacon over the top. Place the partridges into a hot frying pan with a little oil and colour all over, then place in the preheated oven for 12 minutes. Remove and allow to rest.
Next prepare the celery bundles. Cut the remaining celery stick into 10 cm length batons each 1 cm thick. Cut the bacon rashers lengthways and use each strip to wrap approximately 6 batons of celery together. Heat a little oil in a pan and sauté the celery bundles until the celery is lightly coloured. Keep warm.
To Make the Sauce
Place the sherry, white wine, bay leaf and sugar into a pan and bring to the boil, reducing to a syrupy consistency. Then add the game stock. When the partridge is cooked, deglaze the tray with this sauce, simmering for 3 to 4 minutes, then sieve and check seasoning.