"You know, we may just achieve a peaceful settlement," a British diplomat told a reporter 14 1/2 weeks ago on the eve of the Rhodesia peace conference in London. He then hurriedly added, with a twinkle in his eye, "Good God, don't print that."

Those mixed feelings about the chances of solving the prickly Rhodesian independence crisis that has plagued countless diplomats for more than 14 years prevailed right up until the triumphant conclusion four days ago when the Patriotic Front guerrillas agreed to Britain's cease-fire terms.

Yet with the advantage of hindsight, it is apparent that British Foreign Secretary Lord Carrington sensed all along that this ninth international attempt to solve the seemingly interminable problem peacefully presented the best chance for success -- as well as the last.

There is a healthy measure of justice in the basic reason for Carrington's success: after 14 years of declining to take responsibility for the breakaway colony that former prime minister Ian Smith declared independent to preserve white-minority rule, Britain resumed authority in an effort to bring about a settlement.

Taking over responsiblity gave Britain the power to attempt to impose a settlement on the warring Patriotic Front and the black-led government of Bishop Abel Muzorewa that Smith helped gain power.

That in itself would not have worked, however, except for a convergence of other factors. Both sides to the dispute, which boils down to the comparative political rights of almost 7 million blacks and about 220,000 whites, came to the talks weakened considerably by the effects of the escalating 7-year-old guerrilla war that neither side was capable of winning soon.

Neighboring supporters of the Patriotic Front, particularly Zambia, Mozambique and Tanzania, were facing increasing economic difficulties. South Africa, the lone backer of the unrecognized Muzorewa government, was becoming increasingly nervous about the open-ended, fast-rising costs of financing much of the war and was worried that involvement of its troops could lead it into a mini-Vietnam situation.

Carrington had one other advantage. Ian Smith, the leading figure in Africa's longest running indedpendence struggle, had finally been shorn of most of his power. Long the master of hard bargaining with the British, he could no longer dominate British governments torn between public sentiment in Britain for the whites and the knowledge that black-majority rule was the only eventual solution.

Having stepped down as prime minister, Smith was defanged.Instead, Muzorewa, Smith's handpicked successor, was no match for Carrington, who assumed the strongman role in the negotiations.

It was an astounding turnabout for British foreign policy, which had been carried out mainly in the shadow of the United States in the two decades since the humiliating withdrawal of British troops from Suez in the 1956 Middle East war.

The history of attempts to solve the Rhodesian problem is replete with ironies and missed opportunities. One on the supreme ironies, however, is that perhaps the key event in bringing about the confluence of forces leading to a settlement happened more than 5,000 miles away -- with the overthrow of the dictatorship in Portugal in 1974.

Military officers who were fed up with Lisbon's decade-long colonial wars in Mozambique, Angola and Guinea-Bissau that were bleeding the improverished European nation, embarked on a decolonization policy.

In little more than a year, a black-ruled Mozambique gained its independence, depriving Rhodesia of its closest outlet to the sea and giving it instead more than 700 miles of hostile border behind which the guerrillas could operate. The war, until then low-key, could no longer be contained easily.

On the other side of the continent, Angola's impending independence spelled trouble for South Africa's hopes of maintaining white rule in neighboring Namibia, which South Africa controls despite United Nations demands for its independence. The South Africans soon realized that the days were numbered for the white buffer states that separated South Africa from black Africa.

Enter Henry Kissinger, who after years of neglect "discovered" Africa through the entry into Angola of almost 20,000 Cuban troops in 1975-76 to aid a Marxist-oriented government fighting a civil war.

Alarmed by the potential for East West conflict in southern Africa. Kissinger launched a six-month diplomatic initiative, including two trips to Africa to try to end the long deadlock over black-majority rule. Using South Africa for leverage, Kissinger wrung from Smith acceptance of the principle of majority rule.

Even though a conference in Geneva to implement the principle failed, it was only a matter of time before a black government came to power.

The only question was what kind of black government would take over. Smith set out to choose a moderate he could control Muzorewa, who finally took power this year, accepted a constitution allowing whites to exercise control over key areas, such as security and the judiciary.

Britain's election of Conservative Prime Minister Margaret Thatcher in May brought fears in Africa that she would lift economic sanctions and recognize the Muzorewa government. Lord Carrington, however, convinced Thatcher not to go it alone but instead make a new attempt to negotiate a settlement.

Under the umbrella of the Commonwealth summit in Lusaka, Zambia, in August, Carrington switched Thatcher's previous pro-Muzorewa policy, and agreed to the convening of the London peace conference.

Then he began the laborious process of pulling together all the strings attached to the weaknesses that each party brought to the conference table.

Even though there is considerable question whether the agreement will be able to bring about a peaceful Zimbabwe, as Rhodesia will now be called, the guerrilla acquiescence four days ago to a cease-fire means Carrington pulled in the last string and tied the bow, 14 years, one month and 10 days after Smith illegally declared independence Nov. 11, 1965.