They are thought to have been made by fishermen in Japan and East Asia and were bought by sailors as good luck charms or by circus entertainers to display as curiosities.
Early 20th Century scientists were baffled by the specimens, with some claiming them to be mummified mermaids.
They were later believed to be made from the head and body of a monkey sewn on to the tail of a fish, giving rise to the term "monkey fish".
It was not until March 2011 that an X-ray of the Horniman merman (affectionately known as Herman), revealed that the monkey half was in fact made from papier mache.
Using a combination of CT scans, microscopy, X-radiography and 3D printing, the research team have finally managed to piece together exactly how Herman was made.
Dr James Moffatt, a physiology lecturer at St George's University in London, explains the process.