clematis 'Lady Northcliffe'

'Lady Northcliffe' is a climber 1.5-3m high with green leaves and flowers 10-15cm across, composed of usually six overlapping, wide, broadly elliptic, wavy-edged sepals, rich violet-blue at first then fading to mid lavender-blue, and creamy stamens, from midsummer to early autumn and sometimes later; many clematis are visited by bees for pollen, and some also provide nectar