My recollection is that it is Clematis 'Ernest Markham', which is quite easy to grow. As you likely know Clematis love to have their heads in the sun and their feet in the shade. We accomplish this by planting the plant an extra 8" deeper in the ground than it is in the pot. Clematis is one of the few plants that can be planted deep. Have fun.

Thanks for the advice. It's my first year growing Clematis (Josephine, Jackmanii Superba, Ruutel, Victoria and Niobe - :) I couldn't resist them) and I still have them in their pots - am a bit nervous to transplant them into my clay soil. I believe one can keep potting them on into one size larger pot, but the problem with that is remembering to water them almost daily! (We are suffering from El Nino here in S. Africa.) I will have to experiment with at least one of them, amend the soil with compost and plant it deeply, which would of course help keep the feet cool. I am going to look out for Ernest Markham. Thanks again!