Stir in flour and cook for 1 minute, remove from heat and slowly add stout, stock and Worcestershire, stirring until combined. Return to the heat, add meat and stir until mixture comes to the boil. Reduce to a simmer and cook, covered, for 1 hour. Remove lid, stir and simmer, uncovered, for 15-20 minutes or until liquid has reduced and thickened slightly. Season with salt and pepper.