In article ,
says...
Tradescantia spathacea

That certainly looks like it and it sounds the sort of plant that would
be planted up there, (and it explains why the shape of the thing looked
vaguely familiar!
--
Charlie Pridham, Gardening in Cornwall
www.roselandhouse.co.uk
Holders of national collections of Clematis viticella cultivars and
Lapageria rosea