Swing-tail Vickers Merchantman/Vanguard

[Garioch]

I've come across a reference to a proposed swing-tail version of the Vickers Merchantman. It dates back to the British Airways introduction of the TriStar. Merchantmen were utilised to carry new seats,spare etc. however there was a foreseen need to carry spare engines. British Airways Engineering Dept. wanted to modify one Merchantman with a swing tail to carry spare RB211 to stranded TriStars. Sadly they entered into spares agreements with other TriStar operators. Has anyone further info on this,preferably with drawings or sketches. My info came from Airlines & Airliners issue 3.
Regards Andy