Heat 1 tbsp of olive oil in a large saucepan on medium heat. When hot add your onions and cook for 5 minutes, stirring regularly, until soft and golden.
Add your garlic followed by the celery and carrots and cook, stirring regularly for 5-10 minutes until softened.
Add your lamb mince and stir to break down, along with the thyme and oregano. Cook until meat is just brown and no pink remains. Stir in the flour.
Add the bay leaf, tomato paste, soy sauce, red wine, tomato paste, chopped tomatoes, Worcestershire sauce and lamb stock. Season with 1/2 tsp each of salt and pepper. Simmer for 20 minutes, stirring every few minutes to ensure the mixture doesn’t stick. Add in the frozen peas and cook for a further 5-10 minutes, until the mixture has thickened and very little liquid remains. Once cooked, leave to cool for 10 minutes.
Whilst the mixture is cooking, set the oven to 220 degrees Celsius, and bring a large slightly salted pot of water to the boil.
When boiling add the potato to the pot and simmer on medium heat for 20-25 minutes until fork tender. Drain the potatoes and set aside. Combine cream and butter in the same pot on low heat. Add the potatoes back in, turn off the heat and mash until smooth. Season with 1 tbsp each of salt and pepper. Make sure to taste as you go along, mash can need a surprising amount of salt!
In a large baking tray, spoon out the lamb mixture and press down. Cover with the mash, making sure all edges are covered. Top with an even coating of grated cheddar.
Cook in the oven for 25-30 minutes until cheese is golden and the edges of the mash are brown and crispy. Optionally I also popped the grill on and moved the pie up to the top shelf for a further couple of minutes to maximise crispiness.