Hi, it looks like Alstroemeria to me, there are 100s of varieties, some of which are very similar, so hard to say which variety these are, Derek.

Don’t think it’s an alstroemeria Derek. They are all just single stems - all the alstroemeria I know have multiple stems. Of course I may be completely wrong - but I also don’t think an alstroemeria would be so invasive.

no this is definitely Alstroemeria. the one I have is an old variety and it is single stemmed and very invasive. I have managed to get a small piece under control where I want it. the rest have been dug out and composted.

I'd say that it's a Common Daylily (Hemerocallis fulva), can be very invasive.

It is definitely an alstroemeria. It is a lovely long lasting cut flower but an absolute thug in my garden. It takes over a border in no time. I pull out the individual stems as soon as I see them and I have tried killing it off using a contact weedkiller but it is a survivor. If I ever get it under control I would plant it in a pot to keep it in check.