Not quite convinced this is a Great Egret Quoting Morcombe: Great Egret- Gape extends well behind eye Intermediate Egret- Gape is no further back than rear of eye
If you have any other photos, especially one that shows the other side of the face, that would help greatly
I've now posted the only 2 photos I have of it. I was quite a way back but it flew off before I could take more shots. I'm not sure that the eye is definitive. The kink in the neck suggested to me that it was a great.
Usually the gape is clearly one or the other and quite distinctive, kink and some of the other features are slight differences that is often used in conjunction with other features. I will leave this for Chris