The common view of the diplomats was that General Abacha was threatening to hang Mr Saro-Wiwa and his colleagues as a way of drawing the fire of the Commonwealth meeting. As long as they were begging for clemency, the leaders could not be demanding a return to civilian rule in Nigeria. The analysis was wrong.
It now seems likely that the timing of the hangings was unrelated to the Commonwealth meeting. General Sani Abacha and his band of military thugs probably didn't even see the connection, and if they did, they probably didn't care.
This is not just a case of diplomats failing to get the message across. It is a failure of the quiet diplomacy so favoured by the Foreign Office towards bad governments which don't threaten British interests. And in some cases British diplomacy in Nigeria was quieter than quiet. The crucial period in Nigerian politics this year was September, when General Abacha was deciding how much longer he could afford to stay in power. He had promised a definitive statement on his long-term plans on 1 October. Where was the British High Commissioner, Thorold Masefield, in that period? On holiday. When General Abacha announced he was staying on for three more years, the Foreign Office declared it "disappointing".
Equally pusillanimous was the response of the Secretary General of the Commonwealth, Chief Emeka Anyaoku, himself a Nigerian and the architect of the Harare Declaration of 1991 which committed Commonwealth governments to democratic and accountable government. He expressed "concern".
A nice man, always willing to see the best in people, Chief Anyaoku now admits in private he was deceived by Abacha's predecessor, General Ibrahim Babangida, who held an election in 1993 and then cancelled it. Babangida lied to him, he said. But should he have been willing to give Abacha, a far more brutal soldier than Babangida, a chance?
A Commonwealth team which visited Nigeria in July this year recommended that Nigeria should be suspended from Commonwealth membership, yet as late as last week Chief Anyaoku would not even say whether or not suspension - let alone expulsion - was on a list of options for Commonwealth policy on Nigeria. He wanted dialogue.
He may have been influenced by the South Africans. Thabo Mbeki, the Vice President, visited Abuja in July to plead for the lives of a group of people convicted of plotting an alleged coup. He came away accusing Western countries of trying to bully Nigeria and saying that it was up to Africa to draw up its own agenda and not be pushed around by Western countries. "Now we are engaged with that military regime and the solution of that particular problem [the death sentences] becomes South Africa's first substantial point of contact with the continent's most populous nation."
Mr Mbeki did not seem to see the irony in the fact that during the apartheid years he led the attack on American "constructive engagement" with the apartheid regime and continually demanded its isolation and sanctions. One of his strongest allies and helpers in this cause was the former Nigerian head of state, General Olusegun Obasanjo, now imprisoned by Abacha.
It was probably Mr Mbeki's soft approach which led the Foreign Office to override Baroness Chalker's call in September to keep Nigeria away from Auckland. Perhaps, the argument went, if Abacha was lured to Auckland, he could then be ambushed and told clearly to release the alleged coup plotters and return the country to civilian rule. But there was never any chance that Abacha would leave Nigeria. He sent his ineffective and powerless foreign minister, Tom Ikimi, to take the heat.
Can more be done by the international community? Foreign investment in Nigeria's huge oil industry is crucial; US investment stands at pounds 2.6bn and British investment at pounds 3.4bn. There is little chance of economic sanctions until there is a clear threat to the long-term safety of those investments. And there is no guarantee that sanctions would make Abacha come out with his hands up.
But there are many other things which can be done to get the message home. The first is to end quiet diplomacy and spell out publicly what Britain expects of Nigeria's military rulers. Britain could also offer public support for the democratic opposition in Nigeria. The "judicial murder" of Mr Saro-Wiwa should at the very least blow away the Home Office's immigration policy for Nigeria, which suggests it is a "safe country" and Britain should not give political asylum to its dissidents.
And then there are the private European bank accounts of Nigeria's rulers. Since much of the money in them is stolen or obtained corruptly, there is a prima facie case for freezing them and investigating them. Parting the generals from their "pensions" would send the strongest message of all.
n Richard Dowden is on the foreign staff of 'The Economist'