It looks like a white dove Nikki i.e. a domestic bird which has probably gone wild, and is living with the pigeons.
Thanks for replying. I did wonder if it was a white dove. It seemed at home with the pigeons when eating and they weren't bothered even though they outnumbered it.
I have started to notice a pecking order between the varieties of birds which is interesting and was surprised by how nervous the crows were compared to say the magpie. Possibly they usually hunt where they are considered lower down the pecking order.