I was told about this by a friend who is a London policeman. The hook is on Great Newport Street, WC2, near Leicester Square tube station. It is next to the Verve Bar and the old location for the Photographer's Gallery.
Why Is It Here?
This hook was for Metropolitan policemen to hang their cape on, possibly to leave it to dry after rain. In days gone by police were respected more and they could leave their cape here unattended and no-one would touch it.