As I mentioned in passing in a previous shot, there are four bronze reliefs around the base of Nelson's column, representing battles that Nelson had participated in.
This one, which is on the west side of the column, shows the battle of Cape St. Vincent which is one of the early battles of the Anglo Spanish war. It took place on 14 February 1797.
Nelson was not the commander of this battle; that was Admiral Sir John Jervis. Nelson followed Jervis's orders... more or less. Subject to a wide interpretation. With, perhaps, a dash of his own initiative thrown in.
The end result was a fleet of 15 British ships defeating the Spanish fleet of 27, in no small part courtesy of Nelson being liberal with his interpretation of his orders.