A very nice find indeed!
I have seen this photo before
http://www.flickr.com/photos/76971536@N08/7162175700/in/photostream/lightbox/but not with that quality.
To me the "STOR" of CASTOR and the W of the registration looks retouched. Is this in fact another 'boat with a name starting with CA and a registration starting with G-ADU ?
Candidates (from a quick search in Brian's book) are:
G-ADUV CAMBRIA
G-ADUY CAPELLA
G-ADUX CASSIOPEIA
G-ADUU CAVALIER
The aerial masts on the wings is not something I remember having noticed before, but they are visible in the Life photos of CAVALIER but not on the photos of other 'boats I could check. Could this be a retouched photo of CAVALIER?
Cheers,
Anders