Point of order: the 1685 charter was for a fair in April. The mid-June horse fair wasn't constituted till the mid-18c (according to Roud again).

Having never visited the fair, it's very hard to sit in judgement on it. There are conflicting opinions here from people who have attended, and I don't believe it's possible to understand an event like this from looking on a few websites, so I'm not going to offer any further, ill-informed opinions of my own.