I can't see the flowers very clearly, but I think it might be

hymenocallis or something of the same family.

Let's hope someone with experience with this plant will reply to your questions.

Thank you for your reply. I'm not sure it is a Hymenocallis as when I googled the image the flower does not look right. The flower is more of a large full trumpet, though the leaves look similar.
Any other ideas anyone?

This is the picture made into a close up of the flower. It is a trumpet with peeled back tops of the petals.

Perhaps a crinum. Compare to Crinum powellii 'Alba',

Oh thankyou Gardengal.... Yes that definitely looks like it. I can look up the rest on the English RHS website.
Thank you both for taking the trouble to answer, have a great day both of you. Terri

This actually looks like a white amaryllis, by the foliage and the way the flowers bloom from the same stalk.

I 2nd that it's a white crinum.