With Britain's proposal to sell arms to South Africa the dominating issue at the Singapore Commonwealth Prime Minister's Conference, even informal meetings between critics of the policy acquire considerable significance.

The meeting on Friday (15 Jan.) between Canadian Prime Minister Pierre Trudeau and Tanzanian President Julius Nyerere was widely believed to be more important than the set speeches at the Conference. It gave an opportunity to two of the most outspoken critics of British Prime Minister Mr. Edward Heath's "arms for South Africa" policy to discuss tactics for opposing the policy.

President Nyerere has been most outspoken in his criticism of Mr. Heath's policy at the conference. He believes that Commonwealth Governments are bound to one another in decision-making, since the actions of each one must not adversely affect the basic interests of other members.

Mr. Heath has claimed to the Conference that Britain has a right to decide its own affairs, and that the Commonwealth is not a Court of Appeal with a prescriptive right to sit in final judgement on the policies and actions of its members.

Mr. Trudeau's strategy in opposing Mr. Heath on South African arms at the conference is said to hinge on the principle that the British Government must be armed with something to take home from the Conference, if only to make it easier for Mr. Heath to save face.