Now it dates back to the 12th century, but the poor weather has meant this year's Swan Upping ceremony on the River Thames has been cancelled for the first time in 900 years.
It's been a tough year for the local swan population. A virus meant the loss of many of the birds last year. And it's feared this summer's flooding means nests have been washed away.
The annual census - was due to start at Sunbury Lock in Surrey on Monday. Continuing through Berkshire, Buckinghamshire and Oxfordshire this week. Finishing at Abingdon Bridge on Friday.
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School Children in Henley-on-Thames are taking part in the annual census of swans on the River Thames. The Swan Upping has been officially cancelled for the first time in its 900 year history because of recent heavy rain fall.
The annual Swan Upping on the River Thames may have been cancelled for the first time in its 900 year history, but school children are still benefiting from the census.
They have been taking part in a special swan count, to learn about the tradition and the river's wildlife.
The Queen's Swan Maker David Barber gave a talk at the River and Rowing Museum in Henley on Thames.
Swan Upping, the annual census of the swan population on the River Thames, has been cancelled, because water levels on the River Thames are too high. The ceremony dates from the twelfth century and takes place during the third week of July every year.