What Am I Looking At?

Last August I was looking out the window at the front garden. I was disappointed that the floral display wasn't what it should have been. A movement caught my eye and I saw the bird in the picture. It's a pigeon but I am not 100%sure which kind. It looks a young bird and must have fledged earlier in the year. My first thought was that it was a young Woodpigeon but I am nor sure at what age they get their adult plummage including the white on the neck. As you can see this one is beginning to colour up. It was smaller, which made me think it was a young bird, than a Woodpigeon and about the size of a Rock/Feral Pigeon. The light grey/white edge to the wing is beginning to appear. It had the poise of a Woodpigeon but as I say I am not 100% sure it is young Woodpigeon. I haven't seen any Feral Pigeons in my garden or surrounding area. Anyone any idea what it is?