Mary-Ann Ochota discovers the story of the Thames sailing barge - a boat that played a key part in London's history, transporting goods and building materials up the Thames from Victorian times up to the early part of the 20th century. By meeting enthusiasts, current owners and one of the last surviving bargemen, Mary-Ann learns how the barge was designed specifically for the waters and conditions it would be sailing in - the mast lowers to go under London's bridges and the sails are high enough to catch the wind even in the most built-up of areas. Famously though, the barges were once put to sail in alien conditions - they were commandeered to play a part in the evacuation of Dunkirk in 1940. There are still about 30 of these boats on the water - once there were more than 2,000 - though nowadays the emphasis is very much on pleasure, something Mary-Ann experiences for herself when she joins the annual Thames barge match.