The fountains were originally created in 1845, but without the sculptures. At the time the fountains were intended to simply take up space in Trafalgar Square, so that there would be less space available for demonstrators and rioters.
In 1935 plans were approved by parliament to add memorials to these fountains, and also these sea-creature sculptures by McMillan and Wheeler. The bronze statues were completed in 1939, but due to the war all work on Trafalgar Square was suspended at that time.
Work on this did not resume until after the war in 1947. The finished memorials and the fountains were unveiled in October of 1948.
The mermaid statues do not have the traditional single tail, but instead have long and powerful tails as an extension of each thigh.
● The Mermaids of Earth coffee-table book: See page 34 in the book about these sculptures.