The Sin-Eaters tend to be overlooked by the Three Poli because they’re few in number. Not so the Lost. If the leaders of the Three had any concept of how numerous and influential the Changelings who make up the Great Court of London really are, they’d be shocked and more than a little afraid. But they don’t have any concept of it. The Great Court tends to operate almost entirely underneath their radar.
How can that be? It’s worth remembering that the relatively close communication and loose alliance between the three Poli came about largely as a result of an historical accident, the formation of the Temple conspiracy. But for random chance, the Three would likely know as little about each other than they do about the Great Court. Then, too, there was very little Changeling presence in London before the eighteenth century, by which time the Temple alliance had been consolidated and the Three had already drifted into a mindset where they divided the supernatural world into themselves, and everything else.
More importantly, the Great Court operates a deliberate policy of not drawing attention to itself - especially attention from other supernaturals. The Kindred, with their callous, amoral, manipulative ways, resemble the Gentry too much for most Changelings’ peace of mind, and the Uratha are horrifyingly destructive forces of nature. The Mages, in the Great Court’s view, have a deadly mix of curiosity and arrogance that might lead them to ignore or dismiss the dangers of Arcadia and call down the attention of the Gentry with their meddlesome curiosity. And on the rare occasions when the Three have been willing to work together, the sheer power they can wield is terrifying. In 1898, a True Fae known as the Huntsman appeared in London and started stalking and killing supernatural beings for sport. The Great Court knew enough that they were able, for the most part, to avoid him - not so the Three. But when they finally realized what was happening, their counter-attack was devastating. The Huntsman found himself trapped in Windsor Great Park, pinned in place like a fly trapped in amber by the combined magical might of the entire Consilium Council in concert, while the leaders of the Kindred and Uratha tore it apart. After so graphic a demonstration of what the Three were capable of if provoked, the Great Court settled firmly on avoidance as its best strategy for dealing with them, and that continues to be the case to this day.
London operates a fairly conventional Great Court, with leadership alternating between the four Seasonal Courts. A council of four Changelings, known collectively as the Four Who Rule or simply the Four, each reigns as monarch in his or her season, with the other three acting as his or her lieutenants, but in practice they tend to rule as a collective. The Courts are identified by colour - Green for Spring, Scarlet for Summer, Gold for Autumn and White for Winter. The four are known as the "Lord" or "Lady" of their Court while not reigning, or the "King" or "Queen" when they are. So in winter, for example, the White Queen has precedence over the Green Lady, Scarlet Lord and Gold Lady, while in summer the Scarlet King takes precedence over the Green Lady, the Gold Lady and the White Lady.
The strong right arm of the Great Court is a noble order known, in the modern era, simply as the Riders. Its Oath is as unpretentious as its name - it states simply "I swear to stand fast with my brothers and sisters against any who would harm the Grand Court of London or those under its protection". The Riders are the descendants of a much older order that has gone through various incarnations over the centuries - in the eighteenth it was a duelling club - but in the modern era, as the name implies, it's a motorcycle gang - at least to all outward appearances. In reality, its members skill-sets are much more diverse than you’d find in the archetypal group of Hell’s Angels. There are some warriors in its ranks, yes - mainly Beasts and Ogres - but there are also Beast or Elemental cat burglars, Wizened and Darkling computer specialists and mechanics, and even Fairest with a knack for elaborate con games. The Riders are keepers of the peace, defenders of their fellow Lost, and investigators of strange and alarming events, not just thugs and legbreakers. They make it a point to be prepared for any contingency, There are four senior members, known as the Green, Scarlet, Gold and White Riders (always capitalised). The overall leadership alternates between these four with the season, as with the monarchs.
The Great Court meets in a massive Hollow, the Fleet Tabernacle, which is regarded as "community property", held in common by all members of the Court. In the mundane world, there was a river called the Fleet in London, from which Fleet Street takes its name. Covered for centuries, the Fleet is now almost entirely underground, and parts of it have even formed parts of London's sewer system. The Fleet Tabernacle, for some reason, seems to follow the overall shape of part of the underground river (hence the name), but what are caves in the real world have in the Hollow been carved into a huge set of chambers with a fast-flowing river running through their center.Some portions of the Hollow resemble a lavish Victorian gentleman's club, complete with stuffed leather armchairs, Pugin wallpaper and plush carpeting, while others look like the interior of a medieval castle, with battle axes displayed on the walls. Still others look like art deco dance halls and theatres from the 1930s. All, though, have the river flowing through the middle, with beautifully carved little wooden bridges connecting the two halves. In the Throne Room, a huge circular chamber with a vaulted ceiling resembling a medieval Gothic Cathedral, the river expands into an actual circular lake before flowing out again. The throne room has a double dais opposite the doors - the three lesser thrones are on the lower level, in front, and the throne of the ruling monarch is elevated behind them. Illumination is provided by what look like electric lights, gas lights, or torches on wall sconces, depending on the room. The quality of the light, however, is always the same regardless of the apparent source. In spring, it seems to be hazy, pale yellow sunlight, a little diffuse, the kind that burns away an early morning mist. In summer, it brightens to the fierce gold on a sun in the noonday sky.
In autumn, it dims and deepens to the deep, rich red of a setting sun. And in winter, it takes on the silver-white colour of a very bright, full moon. The lighting changes of its own accord, and traditionally, the handover of power from one monarch to another occurs when the Fleet Tabernacle changes its illumination.
Changelings occupy an incredibly diverse range of niches in London. There are Beasts who work as animal trainers, from everything from Guide Dogs to the Blind to police dogs to stunt animals for TV. There are Fairest who work as tour guides, entertainers and even lawyers. There are Wizened who run pubs with the best beer to be had anywhere in the capital, or who work as forensic pathologists with a knack for coming up with results that their colleagues miss, or decorators and artists for the homes of the ultra-rich, or auto mechanics for underworld car-theft-to-order operations. There's one motley of Lost who use their powers to work as stunt performers for TV and movie shows. The various "adult entertainment" industries have more than their fair share of Lost, mostly Beasts and Fairest. So do nightclubs - there are two motleys who combine their various talents - Wizened Brewer, Ogre and Beast Bouncers, Darkling Lawyer and Bookkeeper, Fairest musician - to operate some of the capital's hottest night spots. There are elementals amongst the specialist divers who check out building foundations along the banks of the Thames. There are, after all, very few professions in which at least one Changeling Seeming doesn't provide some advantage. Occasionally, the Riders have to intervene when another supernatural tries to muscle in on Changeling territory - like a vampire trying to get control of a nightclub, for instance - but despite their cover as a motorcycle gang, the Riders do "subtle" very well indeed, and their interference has never yet been traced to its source.