Preheat the oven to 190C/170C Fan/Gas 5. Place potatoes and carrots in a large pan and cover with boiling water. Simmer for 15 minutes or until cooked. Drain, return to pan and season. Mash with 2 tbsp milk.
Heat oil in a large frying pan and cook turkey for 5 minutes. Melt butter in a large pan, add leek and broccoli and cook for 5 minutes until soft but not coloured.
Add flour and cook, stirring well for 2 minutes. Slowly pour in milk and bring to the boil, stirring continuously. Reduce the heat and simmer for 1-2 minutes.
Remove from the heat, stir in lemon juice and season. Add turkey, ham and peas. Pour mixture into a large pie dish and cover with the mashed potatoes and carrots. Bake in the oven for 20 minutes or until the mash is golden brown.