 Considerable skill is needed to pilot "unpowered" barges 'rowed under oars' or "sweeps" and ride tidal river currents alone, up river.The event commemorates the skills of lightermen who moved freight this way along the Thames up until the 1930s and in a wider context it encourages ongoing interest in moving cargo via water and as a way to recruit younger people back into river trades.The teams are normally made up of employees of Thames Lighterage companies, Port of London Authority or are sponsored by local businesses.The best places to view the race are Tower Bridge, London Bridge and Westminster Bridge.