Possibly short of magnesium? give it a handful of Epsom salts

Ok will try that.

Could be black spot, or bacterial leaf spot - try feeding with a specialist balanced rose food, such as Toprose or similar (I'm not a great believer in the epsom salts trick, sorry DRC, lol) and spray with Roseclear 3, (not ordinary Roseclear, the 3 is important) mixed to fungicidal strength.

Thanks, I have fed with Toprose but will get some Roseclear 3

You'll need a sprayer to mix it in too - Double diamond, wasn't that a bitter years ago...

Yes, your right about the bitter.Thanks for the tip.

They now make a Epsom salt feed Bamboo, I am a great fan of it used on on roses since the 70's

Yea, I know loads of people like to use it - I just prefer something with a slightly different composition.

Thanks to everyone for your tips. I think it is black spot and have sprayed the rose bush as advised by local garden centre.