Mystery Flowers

These flowers grow in a garden that I walk past on my way to walk, and I have always been fascinated by them. They are very large, gaudy, showy flowers. I had, on first glance, thought they may even be artificial, but they attract many bumble bees who I'm sure wouldn't be misled! If any of you gardeners out there can tell me what they are, I'd be delighted, as I've never managed to see their owner to ask!