Three emergency personnel were lifted several metres up on a fire brigade aerial ladder platform at around 10:00 GMT, with one person using a megaphone to speak to the man on the ledge.
Negotiations then continued throughout the day and into the night.
The incident began when the man got into the grounds of Parliament, walked up some steps, quickly climbed onto a railing, and up the side of Elizabeth Tower.
At one point he took his shoes off to enable him to climb higher to a ledge. He injured his feet, and patches of blood could be seen on the stonework of the tower.
The man was spotted within minutes by police on the ground, who asked if he was able to get down safely.
Photographs throughout the day showed him sitting on the ledge with the flag and wrapped a traditional Palestinian keffiyeh scarf around the decorative stonework on the tower.
SANGHA KOMMUNE (SSR) 