Identify a climbing rose?

Sorry no photo! Visiting Chastleton House in Oxfordshire this week, I came across a very vigorous rose climbing through a 20ft + holly tree at the end of the garden - in fact there was far more rose than holly! It was not obviously a rose - no thorns, leaves not serrated - and I did not recognise it as such at first. The volunteer gardener said it was but did not know the name. The flowers were yellow, about 25mm across, no scent, and grew in clusters on thin stems. What they reminded me of was a flowering cherry - quite unlike rose blooms, except for maybe a small-flowered floribunda. I have looked online as much as poss. but can find nothing like it.
Any ideas, anyone? Thanks.

PS Really like the look of the GC pages now.

 

Could it be the variety " Smooth Angel "?

 

Thanks for your suggestion, David. I'll google Smooth Angel!

 

Sounds to me like rosa banksiae, vigorous, thornless and clusters of small yellow flowers

 

Think you're right, Lovage. Here's one I googled earlier:-

 

Chastleton House is 10 miles from me and the garden is beautiful:thumb: