Pre heat the oven to 150C fan.
In a large oven proof pan heat the olive oil and then add the shanks and brown all over and then set aside.
Add the onion to the pan and fry gently until it starts to turn translucent, then stir in the tomato purée and flour and cook for a minute.
Add the red wine and bring it to a boil, stirring the flour and purée into the wine until you have a smooth sauce around the onion pieces.
Pour the stock into the same pan and bring it to a boil then add the tomato passata, carrots garlic, bay leaves, and thyme as well as some salt and pepper.
Cover the pan with a lid and place in the oven to simmer for 2 hours, turn the lamb shanks after an hour.
Remove the lid and cook for a further hour to reduce the sauce. Turn the shanks every 20 minutes to prevent them from drying out.