Hadn't noticed the Brit. Think you're right, ex-Eagle of which several came and went 1969-1970. Only 2 candidates in April '69 - G-AOVK and G-ARKB, both of which I first saw during March 1969. One was parked in the "graveyard" as in the picture; the other in the "light aircraft park", where hangar 127 now sits. In the background in this photo taken 7/4/69:-
Can't be sure but I think the above was G-AOVK which was broken up Feb 1970. G-ARKB was sold to Tellair - not sure if it ever appeared at Luton as such, though, unlike G-ARKA, seen here on 23/3/69:-
'KB went to Coventry later in 1969 where it was finally broken up in Nov 1971.