It is mainly old cars. Some drive around the city in procession. The war memorial park is big and the cars cover the whole of the main field. Along with the cars a fair, stalls and shows keep everyone busy. The park also has a small water park feature, a normal park, tennis courts and an on site cafe. This show is celebrating the city's heritage though I've seen other non city manufacturers clubs attend like Porsche BMW ect.
Looks like it's in the first week in June not September and now it seems it's under the name MotoFest Coventry. Don't know how to insert a link here but if you search YouTube for Coventry motor festival you get a good idea of it.