Heat the olive oil in a large casserole dish and brown the diced beef until nicely coloured.
Add the marrow bones to the pan and heat for a further 2-3 minutes.
Remove the beef and marrow bones from the pan and set aside.
Add the chopped onions to the pan and sweat off for 1-2 minutes in olive oil.
Stir in the potato and swede, and cook for a further few minutes before adding the chopped leeks, carrots and bay leaves. Season to taste with salt and pepper and heat for a further 1-2 minutes.
Add the beef and marrow bones back to the pan then pour in enough beef stock to cover. Cover with a lid and transfer to the oven and cook for approximately 2 ½ -3hours or until the beef is tender.
Remove from the oven, spoon onto serving plates and serve with a wedge of crusty bread.