REasson:
I flew the Argosy for 10 years from 1962 until the end of 1971. We certainly had a leader cable aerial fitted just underneath the radome for the CCWR (the nipple on the tit).
None of us ever knew why the hell it was there.
To my knowledge, Benson was never equipped with a leader cable. If it was, then it ended up in Passey's scrapyard very quickly.
On the other hand, I seem to remember that when I went on the Belfast at the beginning of 1972 at Brize Norton, a lot of money had been wasted on sinking useless leader cables into the farmers fields on finals to runway 26.