All whales and sturgeons found on the British coast are the property of the Crown

Since the 14th century all whales and sturgeons found on the coast of the British Isles belong to the Royal family. The law may have been put in place so that the Queen always had plenty of whalebone for her corset stays.

This law is still in force today, however in 2004 a a resident found a sturgeon in Swansea Bay and offered it to the Queen but it was declined. It was given to the Natural History Museum. Perhaps she doesn’t wear corsets anymore.

Source:

https://www.lawcom.gov.uk/app/uploads/2015/03/Legal_Oddities.pdf