The issue threatens to disrupt the smooth proceedings desired by British officials, who are still sighing with relief over the end of the divisive question of sanctions and South Africa, which plagued Commonwealth gatherings throughout the Thatcher years.
But there will be no easy way to navigate between the Scylla of French pride and the Charybdis of international outrage. New Zealand, which is hosting the November meeting of heads of government, stands in the forefront of those Pacific nations enraged by President Jacques Chirac's decision to resume nuclear testing at the Mururoa atoll.
The New Zealand and Australian governments can count on support from other regional members such as Malaysia. New Zealand's Prime Minister, Jim Bolger, will be chairing the Auckland meeting and is certain to demand that a condemnation of the French appear high on the agenda.
Britain has come into the firing line because of its flat refusal to condemn the French tests and its public line, first enunciated by the Foreign Secretary, Malcolm Rifkind, that "this is a matter for the French government".
So indignant was the tide of Pacific opinion that greeted this pronouncement that within a day the Foreign Secretary had subtly altered his language on the issue. The tests were, he discovered, something "which the French government will want to explain and to justify". This is diplomatic code for: "we don't want to annoy the French but they certainly needn't expect us to stand up for them in Auckland". The Foreign Office obligingly agreed that it "understood" the strong feelings aroused in the region.
Quick to detect an opportunity to put Mr Rifkind on the spot, the shadow Foreign Secretary, Robin Cook, weighed in with a public declaration of support for the protests by Labour parties in Australia and New Zealand. "The silence of our government is all the more conspicuous as we are the still the colonial power for the Pitcairn Islands - which is the immediate neighbour to the testing zone - and have strong ties with Australia and New Zealand, who are leading the resistance in the South Pacific," said Mr Cook.
"John Major will find himself out of favour and out of step at the Commonwealth conference, which, embarrassingly for him, will be held in the middle of the test programme."
Mr Cook's optimism may prove unfounded. The Foreign Office had always coupled its non-condemnation of the French tests with the hope that France would join the other powers in agreeing to the Comprehensive Test Ban Treaty (CTBT) expected next year. Britain itself had not made its position entirely clear on the issue, leading critics to suspect that the Government secretly hankered after the odd test or two before then, perhaps even for a low-threshold loophole in the treaty itself. (How, ask sceptics, should you define a very small nuclear test?) But on Thursday the British ambassador to the Disarmament Conference in Geneva, Sir Michael Weston, arose to tell fellow-diplomats that the UK "sincerely accepted. . . to negotiate a complete ban on nuclear tests." Insiders say Sir Michael's speech was cleared by ministers only at the last minute and after heavyweight discussions among the arms control professionals who are determined not to negotiate away a single concession involving Britain's own nuclear deterrent if it can be avoided.
But Sir Michael was authorised to take a position of utmost clarity. "I wish now to put on record my government's position that the CTBT should not permit any nuclear test explosion involving any release of nuclear energy, no matter how small."
So the British delegation can go to Auckland with a squeaky-clean record on test ban diplomacy. It may not, however, be enough to avoid the testing question of whether Britain chooses to annoy its fellow Commonwealth members or its French partner during the proceedings.Reuse content