They’re an interesting social phenomenon that started, as you say, in the upper classes but become common with the middle class right up until the 1950s. There are quite a few still operating today, not just in Britain, but in the US as well as a lot of commonwealth countries. Aristocrats in this time were primarily based in the countryside but would visit the City for business or events occasionally. Their relationship with their club would be kind of like an exclusive 5 star hotel kept on retainer. They could expect to have all of their ‘service’ needs taken care of just as they would expect of their servants back home. They could host parties or events on club premises as if it was their own house. Over time these clubs would become the main way for young aristocratic men to socialize with each other. Clubs were for the 1% of the 1%

The 19th Century was a period of increased urbanization and saw the growth of a huge middle class in London. The new middle class copied a lot of characteristics of the aristocracy including aspiration to belong to a club, leading to the ‘Golden Age of clubs’. These are the clubs that you’re reading about. You can think of them as somewhere between a frat for adult, the freemasons and a full service hotel. Individual clubs may have had specific rules but generally you would become a member by being referred by an existing member. During the golden age of clubs you might choose you club based on your military service (The Guards club, The Army and Navy, the RAF Club), your politics (The Beefsteak Club, The Reform Club), your School or university, your job or trade, (The Arts Club, White’s for doctors). You were expected to only be a member of one club, but they would often socialize with each other and it was common to meet friends for engagements at different clubs.

Generally the club was like having a second home. A gentleman could eat there, relax, play parlour games, gamble, network and gossip. Some clubs encouraged networking and dealing but others banned all business on pain of expulsion. The club would maintain accommodations in case a member needed to stay. Most clubs would have a separate dining area where members and non-member guests could meet but the rest of the club was off limits to outsiders, especially women. Some gentlemen could spend years at a time staying at their club, if their business or residence was overseas.

Hope this helps!

A Flight to Domesticity? Making a Home in the Gentlemen’s Clubs of London

Think of a modern American country club. They are basically the modern descendants.

A gentlemen's club was an organization created to provide socialization, fraternity, and minor benefits to its members. Generally they would have been organized around a profession, interest, or other common bond. Being accepted into a club meant arriving on the social ladder. It was basically a home away from home, and apart from those pesky female relations.

What were these clubs? Did they have a proper name?

Collectively? Gentlemen's club, or even more simply just club. Individually yes, hey had differing names.

How did a man become a member?

It depended on the club and the man. In general a sponsorship would be required. You needed recommendations and a chance to prove you would be a proper fit and benefit to the other members. Sometimes the waiting lists for certain prestigious clubs were decades long. Much like country clubs today, exactly how hard it was to join depended on the exclusivity of the club.

How would a man choose which one of several clubs to become a member of?

Often it was a question of which club one could get into. Friends or family connections were often required. Others were more professional organizations. So a young doctor or lawyer might join his mentor's club. A lot of the clubs were very exclusive so a young man might have to inquire after several clubs before he found one that would take him. Being able to show off your club to potential friends was an important part of society. Being able to bring in important guests was an important part of being a good club member. Club members could rise or sink in social standing as a body. So both sides were as picky as they could afford to be.

What would he do as part of the club? Literature seems most often to describe bachelors having dinner there.

They were a mix of social venue, boarding school, and home away from home. The clubs had parlors and libraries. Gambling and other parlor games were popular. The club might provide some small entertainment like a scientific demonstration or recital for the club members and select guests.

They almost always had kitchens and dining rooms. They served the same kinds of roles that restaurants or hotels do today for business meetings and power lunches. Taking a prospective client to your club to wine and dine him was a very proper practice. For a bachelor it was also an alternative to eating alone. Meals were considered social events and eating alone would be seen as an eccentricity. Clubs provided an easy outlet to make sure one never had to eat alone.

Most (but not all) clubs also had bedrooms. For a country gentlemen, having a club meant you had a home in London, when you went there. For gentlemen who regularly lived abroad it served the same purpose. No simple hotel could provide the comfort and fraternity of a club. Many of the clubs specifically focused around military and government officials and decorated appropriately. So when visiting London from India, members of those clubs could spend their time with men who had similar experiences.

For young gentlemen bachelors the club might actually serve as a home full time. It was a cheaper way to establish a household, and provided a higher state of living than they could achieve on their own, while relieving them of the need to actually manage a household.