Use a pressure cooker. Seal the meat in a small amount of oil, add onions, garlic, bay leaf marmite and stock. Bring to pressure then turn off the heat and leave the pressure cooker on the stove and allow to come to normal pressure so that you can remove the lid. Do not remove the pressure manually.
Add the tomatoes, potatoes and other vegetables except the peas, stir well then pour the lentils over the top. Do NOT stir the lentils in at this point or they will burn onto the bottom of the pressure cooker. You have been warned!
Pressurize the cooker again, and again allow to come to normal pressure.
Test to check that the vegetables are cooked; if not, re-pressurize.
Add frozen vegetables and season to taste with salt and pepper.