horn not working?

I have a 2003 S type Jag. For some bizarre reason the horn has decided to stop working. There is power going to the relay/or a current. The relay is ok as is the fuse. Tried changing both and it makes no difference. The horn works because if you switch it at the horn itself it works. But something is not right. Does it just have 1 fuse and 1 relay? Am I missing something?
Thanks