Sometimes research can be awkward this was one of them. Asked to put a page in the Roll of Honour for Donald, I could find no traces of him until I tried McDonald and then ‘bingo’, many KEW files.
He now has a page under MacDonald in the Roll of Honour, ‘Site Memorial’ section:-
http://www.roll-of-honour.org.uk/m/html/macdonald-donald-walker.htm
Information
Joan MacDonald
James McHarg Miller
‘Sinking of the Lisbon Maru’ by Tony Banham
KEW:- WO 361/1744, WO 361/1744/2, WO 392/25, WO 345/33, WO 361/1964, WO 361/1963