Can anyone please identify this flower

Would be easier if we could see some of the leaves as well as the flower. Is it an indoor or a garden plant?

I would think this is bind weed, the dreaded garden pest

Could be oenothera speciosa. This looks as if it has overlapping petals which bindweed doesn't have - very similar.

Many thanks. as Wagger above speculates, I have identified the plant as Oenothera. berladieri speciosa, The Mexican Evening Primrose. Thank you for your answers, which are much appreciated