Cyril himself says that he wrote the tune for Sammy's Bar (1958).  There are resemblances to phrases from, for example, Banks of Green Willow (the tune popularised by George Butterworth) and Shenandoah, but that doesn't necessarily imply any conscious (or even unconscious) borrowing; often, such resemblances are just the mark of a successful composition in the traditional idiom, which is what I've always taken this to be.  He also remarked (1990) "Those of my spies who've been lucky enough to revisit lovely old Malta tell me that Sammy's Bar, at the head of Pieta Creek, has been demolished.  In the '50s the Submarine Depot Ship HMS Forth was just around the corner, and the bar sold very cheap, but very strong, white wine.  It was cramped, but the acoustics were marvellous, and it became a favourite venue for me and my guitar.  The tale, though, is totally fictitious."