Cut the bell pepper into long strips.
If the mushrooms are big, cut them in half.
Chop the onion and mince the garlic.
Heat the oil in a heavy-based saucepan and fry the onion for about 3 minutes. Add the garlic, green pepper and mushroom. Cook for another 3 minutes.
Add the spices, stir for half a minute.
Add the tinned tomatoes, tomato purée, and the drained beans. Season with salt & pepper, add the sugar and cook for about 20 minutes .
When the sauce thickens, it's ready.
Serve warm with rice or flatbread.