Lange thought the US saw him personally as the stumbling block to progress and he was ready to resign if it would help get a solution.
"Mrs Thatcher ignored this and repeated firmly that if New Zealand wanted [ship] visits, it would have to make them possible," Hensley says in his book, Friendly Fire.
In terms of offering to deal with the British in a different way to the US, Hensley believes Lange was just floating something to get him through the lunch with Thatcher, which he had been nervous about.
"It was a bit of a surprise because this was the very thing we were refusing to do for the Americans," Hensley told the Weekend Herald. "And had we given the Americans that right, of course we'd have been like Denmark and the others and visits would have continued.
"She on the whole didn't respond, but he said 'well, New Zealanders see the British as different from the Americans and we wouldn't dream of asking the British what they had on board'."
Lange's relationship with Thatcher could have got off to a worse start were it not for Bruce Brown, the deputy High Commissioner in London at the time of the Prime Minister's speech at the Oxford Union debate about nuclear weapons. According to Hensley's research, Brown not only removed some potentially offensive references out of the speech that Margaret Pope had drafted, but he removed some ad-libbed comments from a transcript prepared for Thatcher ahead of a subsequent meeting with Lange.
Hensley was the head of the Prime Minister's Department in the first term of the Fourth Labour Government. The Cabinet led by Lange's successor, Sir Geoffrey Palmer, vetoed Hensley' s appointment as Secretary of Defence, although the National Government elected in 1990 approved it.
Hensley's book is not the first on the subject but it is the first that has been written with access to official papers from the US, Britain, and Australia as well as New Zealand.
The only time Hensley lapses into "I" is his account of heading to Washington to try to salvage the intelligence relationship.
"I wanted to make it quite clear that this was not memoirs ... This is history, not memoirs."
"People will say 'oh well, that is the sort of book you'd expect from that guy - it's the revenge of the officials on David Lange'.
"Well it isn't. It's the revenge of the facts."
Palmer told the Weekend Herald that though Hensley was a skilled historian and had done meticulous research, "his point of view is that he didn't like the Government policy and he still doesn't".
Palmer also disputes the claim in the book (based on US and NZ officials' accounts) that his own trip to Washington to try to salvage a solution after the Buchanan refusal killed off any possibility of a negotiation because he lectured the Americans on their own constitution. "I was there. He wasn't and I have precise notes of what I said at those meetings ... and they are not preachy."
Palmer will give his own fuller account of what took place in his memoirs, which he expects to be published around Christmas.
In hindsight, says Palmer, there was never a way through the Anzus dispute.
"It takes two to tango and the Americans, I think, felt we would change our policy if they exerted enough pressure on us. I couldn't see any flexibility in the meeting I had in Washington with them."
Hensley believes that things could have gone differently for the Buchanan visit and that New Zealand's anti-nuclear policy could have co-existed with America's "neither confirm nor deny" policy.
"The Americans' position was that a public judgment on the acceptability of one their ships was unacceptable and it was not acceptable because of all their other allies," he says.
"But they could have accepted something in which the Prime Minister said 'we are having a visit from USS Buchanan and we welcome it as being in conformity with New Zealand policy'."
Hensley concludes that events leading to the collapse of Anzus were New Zealand's biggest foreign policy mistake.
"And the evidence for that is, immediately after we had made it, we set about for the next 25 years trying to get back to more or less where we started. That speaks for itself," he says.
"But the legislation is now part of our national identity. We built ourselves a new national identity on being clean and green and non-nuclear so that has become as much part of us as hakas and gumboots."
The reference to Lange broaching the issue of resignation on June 5, 1986 was gleaned from British papers on the Anzus row.
Hensley says it was a revelation to him during the research just how much work the British put in to trying to find a way out of the Anzus standoff.
They weren't part of Anzus but they were allies of the US and were part of Western security alliances, including Nato. Howe worked with the US to find a form of wording in the anti-nuclear legislation in 1986 that could be acceptable to the US and prevent New Zealand being suspended from Anzus.
The British sent their defence force chief, Sir John Fieldhouse - whom Lange joked had left his office preceded by an aide carrying his hat on a silk cushion.
He was followed a couple of months later by a junior minister at the Foreign Office, Baroness Janet Young (whom, Lange quipped to reporters, had left her broomstick at home).
Both Britain and US objected to the proposed New Zealand legislation that allowed the Prime Minister to decide whether a vessel was nuclear armed or not and saw it as a breach of their policy.
As Howe said in a letter to Lange: "A declaration by the Prime Minister would inevitably imply that a ship was not carrying nuclear weapons, and Britain would either have to comply or deliberately deceive."
As the stand-off continued, New Zealand still refused to leave Anzus but anticipated a suspension in August 1986 at meeting between US and Australia in San Francisco.
Australian Prime Minister Bob Hawke was very keen for any action against New Zealand to be taken after his own party conference in July because his own members were getting restless over nuclear weapons.
The book shows there was much more sympathy for New Zealand from Britain than Australia, whose Foreign Minister at the time, Bill Hayden, described New Zealand's policy as confusing, saying: "At times New Zealand is like the cross-eyed javelin thrower who doesn't win any medals, but keeps the crowd on its toes." (Lange's response, was that the only thing Australia was known for was the boomerang.)
The end came sooner than expected. The US Secretary of State, George Schultz, effectively pronounced the suspension from Anzus after meeting Lange in Manila in June 27, 1986 at an Asean meeting.
"We part company as friends, but we part company as far as the alliance is concerned," he told New Zealand reporters after the meeting.
Lange was surprised at the sudden decision, making the point that the British had been willing to accommodate other allies such as Spain and Denmark, which had non-nuclear policies.
Schultz replied that that though Denmark, Spain and Norway had anti-nuclear policies, they did not rule out ship visits. New Zealand, on the other hand wanted a way to accept or reject visits.
Hensley then describes in the book a part of the discussion, which has either been expunged from the US record or never appeared.
"To the surprise of his hearers from both delegations, [Schultz] added that New Zealand had to accept that from time to time there would inevitably be nuclear weapons aboard the occasional visiting ship."
It was seized upon by activists later as confirmation that even if a compromise had been reached, the US would have disregarded the policy.
