For over 150 years, its use was debated; in 1998, the Royal Society for the encouragement of Arts, Manufactures and Commerce (RSA) commissioned three contemporary sculptures to be displayed temporarily on the plinth.

The fourth plinth on the northwest corner, designed by Sir Charles Barry and built in 1841, was intended to hold an equestrian statue of William IV but remained empty due to insufficient funds.

These were: A committee convened to consider the RSA's late-1990s project concluded that it had been a success and "unanimously recommended that the plinth should continue to be used for an ongoing series of temporary works of art commissioned from leading national and international artists".

[1] The London-based American harmonica player Larry Adler jokingly suggested erecting a statue of Moby-Dick, which would then be called the "Plinth of Whales".

[42] In Sir Arthur Conan Doyle's 1912 novel The Lost World, the narrator speculates that Professor Challenger "in his fancy, may ... see himself sometimes, gracing the vacant pedestal in Trafalgar Square".