In a deep heavy-based casserole pan with a lid (and which can go in the oven), heat some oil over a medium heat. Add the onion, carrots, and leek, then fry for 5 minutes until starting to soften. Add the garlic and fry for a couple more minutes.
Add the beef, flour, tomato puree and worcestershire sauce. Turn up the heat and brown the meat, stirring frequently. Add the wine and bubble to reduce for about 1-2 minutes.
Add the stock and the thyme.
Bring up to the boil then turn down to the lowest setting until the stew is barely simmering. Put the lid on and simmer for about 3 hours on the hob or 3 hours in the oven at 140c.
Once cooked, taste and season. Serve on top of jacket potatoes or with mashed potatoes.