I didn't see this bird initially, but could hear something singing from the hedgerows that I didn't immediately recognise. They are elusive little birds, moving up and down the hedgerow feeding and singing. They can be spotted flying from tree to tree, but once they land they disappear into the foliage. These photos are a rare glimpse.
The Lesser Whitethroat differs from the Common Whitethroat mainly in colour - they more grey rather than brown, and a little smaller.

Sometimes it is very difficult to recognise a bird by sight. A far more reliable method is to listen to the bird's song. In this case, the Lesser Whitethroat looked very similar to the more common Whitethroat, but its song is quite different...