Found by the house owners in their garden (incidently the same garden that hosted the recent Collared Flycatcher) and seen by a few locals only during the afternoon. Initially ID'd as an Eastern Crowned Warbler until the last observer of the day pointed out it didn't have a crown stripe!
Sadly kept quiet due to access problems which would have meant large crowds were a real no no. It was gone the next morning so most of us wouldn't have seen it anyway.
See the Portland Bird Obs website here
Apparant Pale-legged Leaf Warbler, Portland (copyright Portland Bird Obs)