The flags on the Cenotaph in Whitehall are the insignia-style emblems representing Britain’s armed services, displayed on the sides of the monument rather than national flags. They are meant to symbolize the Army, Navy, and Air Force (and related service components) and to reinforce the Cenotaph’s function as a national war memorial. Key points:

• The flags are positioned along the sides of the stone monument, accompanying the central inscription and laurel motifs.
• Historically, Lutyens designed flags to be carved or depicted in stone, but cloth flags were ultimately used in the public display, and this practice has continued with periodic renewal.
• The specific arrangements and meanings have been explained in architectural histories and conservation sources, which note that the flags convey military associations and national remembrance rather than serving as a straightforward national flag display.

If you’d like, I can pull authoritative sources and provide precise descriptions of which flags appear on each side and how they’ve changed over time.