Unusual redpoll

This striking Lesser Redpoll has been caught twice in Derbyshire. More remarkably though, it was ringed by Bryn Roberts in 2009 as a 5 with only two white greater coverts and then the photo was taken by Geoff Mawson when it was retrapped it this year. I had never realised that leucism could be progressive like this. Anyone care to comment? Thanks to Jim & Jack Street for passing it on.
Pete