Boats with people in uniform go to the Thames on an important mission. The teams will have to count all the swans that are considered the property of the king in the UK. The annual tradition dates back to the XII century. The chief swan keeper David Barber is responsible for the calculation. A lot of spectators usually come to watch the event. It may seem to someone that this tradition has long been outdated. But it is of practical importance: it helps to monitor the health of birds. Barber served Queen Elizabeth II for many years, and last year he came under the command of Charles III. It will take the team about five days to complete the journey up the Thames.