Heat the 50ml/2fl oz oil in a large saucepan, add the bacon and cook over a medium heat for 5 minutes. Stir in the flour and cook, stirring, until the flour turns nutty brown. Remove from the pan. This mixture, known as a roux, will be used to thicken and flavour the gumbo.
Heat the extra 2 tablespoons oil in the saucepan, add the onion, cayenne and peppers, and cook, stirring, over a medium heat for 5 minutes or until the onion is golden brown.
Add the okra, bay leaf and tomatoes to the saucepan, and bring to the boil. Reduce the heat and simmer for 30 minutes. You may need to add water if the mixture is too thick.
Stir the prawns and the roux into the mixture, add the Tabasco and season with salt and pepper. Cook for 5 minutes or until the prawns are cooked. Serve hot.