I have just seen the images of yesterdays leucistic Ortolan at Landguard. An amazing looking bird but undoubtedly an Ortolan, in my view. I gather it was calling typically. Not sure why you would consider it a likely escape though?
This brings to mind a very washed-out example that Richard Cockram and I found in the Bill quarry on 12th October 2007. The bird, which was not as pale/unmarked as the Languard individual, virtually lacked all yellow, olive and russet tones to its plumage.
Some years ago there was a resident leucistic (white) male Corn Bunting at the Bill which, I recall, may have succumbed to a Merlin. I would have to go through my notebooks to find out which year since there appears to be no mention of it any PBO report!
Cheers, Grahame Walbridge.