What is this shrub ?

I suspect that it's a Viburnum opulus, Hywel - commonly called the 'Guelder Rose'. It should have some leaves with three lobes; I can't spot any in your photo - hence the slight doubt.

Thank you Spritzhenry.
Next time I'm up that way I'll chack the leaves.
I stopped there to take a photo of a nearby castle. I've never noticed it before and wondered what it was.

I don't think it is Opulus either, but some other Viburnum. As well as the leaves being the wrong shape , the berries don't look like Opulus.It is so easy to know what is not but harder to know what is !!!!! Was the castle Carreg Cennen?

Yes Wyeboy it was Carreg Cennen. I put photos of it for someone on GOY who asked me about Welsh castles.
Thanks for answering my question.

Viburnum lantana, Wayfaring Tree maybe?
http://www.floralimages.co.uk/pviburlanta.htm

I've checked it out and I believe it's a Wayfaring tree V. lantana.
Thanks for all your help.