In Bloom (but what is it?)

Arrive back in the UK late yesterday afternoon. The house sitter had done a brilliant job and our cats were stress free (they've never liked going into the cattery).

The only hiccup was the stream pump appeared to be blocked up with algae or something similar, therefore no water cascading down!!! So old jeans and t-shirt on, I spent the next hour unclogging it ... success.

Whilst lying flat on my stomach head down the reservoir, I notice this beautiful plant in full bloom right beside me. Truthfully I can't remember what it is but thought it so pretty it would be today's blip.

Does anyone know what it is please?