In medieval times swans, like the sturgeon, were reserved for the table of the king and a few other privileged nobles and clerics. The Hospital was built close to the River Wensum and two creeks extended into the precinct from the south bank.
One, or maybe both, of these were navigable and allowed small boats to come to staithes within yards of the buildings and unload food, fuel and building supplies.
One of the creeks also fed fish ponds and both probably attracted many pairs of swans. In Stuart times swans continued to be protected birds and Nicholas Salter was locked up in Norwich Bridewell for three months for destroying a swan’s egg in 1664.
St Giles’ Hospital acquired the right to herd swans soon after its foundation. Every person or institution in Norwich having this right had to mark their swans with a distinctive sign lightly cut into its beak. In August each year a ‘swan-upping’ took place on the river when ownership of all of the cygnets was established. A chart in the Refectory shows 72 of the marks used in Norwich, some of them belonging to the Hospital.
In order to make a cygnet fit for table it has to be fed on grain for some time and to do this it has to be confined. In the case of the Great Hospital, the famous Swan Pit built for the purpose in 1793 by William Ivory was in use until its closure was forced by the shortage of grain caused by the Second World War. By this time the Hospital was earning a worthwhile income supplying oven-ready swans for the tables of those who could afford them (one was always sent gratis to the King at Sandringham at Christmas). No doubt their feathers and down provided a valuable by-product.
The Hospital also supplied live swans to customers all over the country, the birds being dispatched in wicker baskets by rail to be met at a specified time at a local station. In 1937 the cost of the swan was £1.5s (£1.25) and carriage was extra. The Great Hospital Swan Pit is the only one to survive in Britain and is a ‘listed building’.
The information about this unique feature was taken from > Link
... where some early images are also included.