Fry the minced meat, diced onion, carrot and swede in a large frying pan or wok until mince is browned, about 6 minutes. Season well.
Add the flour and mix well. Add the red wine and let it bubble for a few minutes. Add the beef stock and mixed herbs and a good glug of Worcestershire sauce. Simmer for 30 minutes.
Preheat oven 180 C /160 C fan/ Gas 4.
Meanwhile boil the potatoes in lightly salted water until cooked. Drain well. Add the milk and 50g butter. Season and mash.
Saute the leek in a pan with the rest of the butter. Set aside.
Put minced meat into a large baking dish. Mix half the leek into the mashed potato and put on top of the mince. Place in oven and bake for 25 minutes. Remove and add remaining leek to top of pie. Place back in the oven and bake for additional 10 minutes.