Look at how people search for these and one thing stands out. They do not search for a run club, they search for a Tuesday run club, or a Saturday one, or a Wednesday one. Almost every popular refinement is a day of the week.
That is worth pausing on, because it tells you what people are actually shopping for. Not exercise. A standing commitment with the same faces, on a day they can protect.
What actually happens at one
Most London run clubs work the same way. People gather at a fixed point at a fixed time, someone says a few words, the group splits into pace groups, everyone runs a loop of three to five miles, and a proportion of people go for a drink or a coffee afterwards. The social part is mostly before and after, not during.
You do not need to sign up, pay, or be fast. You do not need running clothes beyond something you can move in. Nobody will time you.
The thing that decides whether you go back
Ask whether the club runs a slow group with a designated person at the back.
This sounds like a small operational detail and it is the most important question you can ask. When parkrun introduced a formal "parkwalker" role, a volunteer whose job is explicitly to be last, participation among walkers rose by more than half at the venues that adopted it, against about a fifth at venues that did not. A study across dozens of venues and tens of thousands of participants.
The effect is not about walking. It is about permission. Knowing there is a named role for being the slowest person removes the fear that stops most people attending in the first place.