It is that time of the year again for a stock take of the UK's Queen Elizabeth's swans in the River Thames.

This annual event of recording and examining the cygnets and swans, known as Swan Upping, has been carried out since the 12th century.

In the past, the practice was all about food as swans were highly valued and a very important food source. Cygnets were served up at banquets and feasts.

Today, swans are protected and not eaten, so the exercise is about conservation and education.

Swans are lifted from the river onto skiffs, the cygnets taken ashore, measured and weighed. All birds are checked for disease or injuries. Those needing medical attention will be looked after by a vet.

The five-day census is highly popular and draws crowds of observers to watch the action.