This is the Canary bellflower, Canarina canariensis, which has no close living relatives. It scrambles over things, like bindweed, with a stem up to 3 m long, and produces these lovely flowers in December. All the examples I’ve found so far this year are in Los Tilos, on the road up to the visitor centre.
Sheila came to La Palma with a six month contract and has stayed 24 years so far. She used to work as a software engineer at the observatory, but now she's a writer and Starlight guide.