Any question answered...

I have a slight 'click' on my bike when pedalling - once every rotationg of chain. It's felt as much as heard.

The bike's 10sp (Shimano 4600 mech, 5701 cassette, 6701 chain with a quick link).

Things I think are OK;

• pedals
  
• bb
  
• chain wear, quick link, stiff links
  
• cassette isn't worn, it's secure on freehub and the freehub is clean and not visibly damaged, it's an Ambrosio Zenith hub
  
• jockey wheels spin OK and have all their teeth
  
• chainring isn't warped or anything
  
• freehub seems to sound OK and I can't detect any movement - although it's not easy to put much force through to test.
  
  

Any ideas what I'm overlooking?