Some do require it and some don't.
You really need to know it's name and then, you/we can tell you which category it falls into .... the 'to prune' or 'not to prune' group.

I wrote a blog about pruning clematis - you'll find it if you click on 'C' at the bottom of the page, then on 'Clematis plants' and scroll down to the blogs.. I hope it helps.

If it didn't flower till end of June and remained in flower that long, it's probably a jackmanni or viticella type - if it is, prune it NOW down to about 2 or 3 buds from the base. Should by done by mid Feb.

Thanks for your suggestions,I had a feeling it needed pruning