Melt the butter in a large saucepan over a medium heat and add a splash of oil. Lightly brown the meat in the pan, then stir in the Marmite and Worcestershire sauce. Turn the heat up and keep stirring as the meat browns further. It will release lots of juices – just keep stirring and cooking until all the liquid has evaporated.
Throw in the chopped veggies, bay leaf and rosemary sprig, place a lid on top and sweat gently on a low heat until softened.
Stir in the flour and, after a minute, pour in the stock. Season well with salt and pepper and bring to the boil. Turn the heat down to a simmer, add the pearl barley and cook gently for about an hour.
Take the pan off the heat and discard the rosemary sprig and bay leaf. Whiz the soup with a hand-held blender for a couple of seconds, so it thickens, but there are still some chunky bits in it, then give everything a good stir. Serve with hunks of soda bread.