Following the first 2 Black Buck missions, Black Bucks 4-6 were planned as SEAD missions (Black Buck 3 was cancelled due to weather). The crew of BB4, 5 and 6 were aware of the Soviet AGI moored some 15 nm to the south of Ascension Island and were not naive about its activities or motives. However, when BB5 broke the radar horizon at around 40 nm with a climb to 12 000 ft from low level, it appeared to the crew that they had achieved an element of surprise (due to the response of the ARI-18228 Radar Warning Receiver). Black Buck 6 was a little different and the crew always held a suspicion that their arrival had not been totally un-expected.
Some 30 years after the event, information came to light on this forum that the crew of Grupo de Artilleria Antiaerea (GAA) 601, manning a Sky Guard Fire Control Unit, had indeed received a tip-off. Unfortunately, that information did not prevent the destruction of their unit and the death of 4 of its crew.
Roll the clock forward again to 2014 and this forum was used to publicise the visit of a number of Argentinian Air Force veterans to the UK last summer; I think the historian arranging the visit was a gentleman named Andrew Smith who resides in Budapest. The Super Etendard and Sky Hawk veterans, along with the commander of GAA 601 back in 1982, withdrew from the visit at late notice. The Vulcan 597 crew never did get the opportunity to discuss those events with the Sky Guard veteran, discussions that may have clarified their assumption and suspicion one way or the other.
For those interested in the previously un-told story of Black Bucks 4, 5 and 6, the truth of those 3 missions can be found in Tony Blackman's book, Vulcan Boys (link here).
http://www.blackmanbooks.co.uk/vulca...apter%2014.pdf