To commemorate sailors who had died at sea in the First World War and had no known grave, an Admiralty committee recommended building memorials at the three main naval ports in Great Britain: Chatham, Plymouth, and Portsmouth.

Identical memorials at all three sites were designed by Sir Robert Lorimer, with sculpture by Henry Poole.

Each corner projects as a buttress, surmounted by a statue of a reclining lion, beneath a stepped base to the obelisk.

The four-sided obelisk tapers slightly to a stepped top with an elaborate finial with corner ships prows and bronze supports to a verdigris copper ball.

Names of those lost in the Second World War are recorded on panels set into the low walls of an enclosure added to the north, leading to a barrel-vaulted pavilion on each side.