After dark in one of the Cuban capital’s few privately owned restaurants, or paladares, the conversation turns cautiously to politics.

With President Castro so unwell that he may miss today’s huge military parade to mark his 80th birthday, Cubans are on the brink of a new era when key decisions will no longer be taken by one man alone.

“It’s been more than 40 years the same. No nobody knows what will happen. There is great uncertainty. People want liberty — more liberty,” says a man who works in a state-owned metals factory.

His friend, a cook, comes over and whispers in my ear: “Fidel’s a user. Cuban money is worth nothing. To get clothes, beer, perfume, you need convertible currency. All you can buy with Cuban money is rice and beans and cooking oil.” Scratching his bulging belly, he consoles himself, however. “But I eat as well as Fidel — and I’m going to live on.”

Hundreds of blue plastic garden chairs have already been put out in rows in the Plaza de la Revolución for dignitaries to review the troops at today’s parade. Shiny tanks and missile launchers have already been rumbling through the 11-acre square in rehearsals.

A line of more comfortable chairs has been placed at the foot of the colossal statue of José Martí, the Cuban nationalist hero, the spot from where Mr Castro has delivered many of his legendary, almost day-long speeches. It will be the first military parade in Havana for a decade and the state-run papers report that 300,000 people have been mobilised to march. Yet it remains unclear whether Fidel Castro, the world’s longest-serving President, will be able to attend.

After fainting in public in 2001 and fracturing his kneecap and elbow in a fall in 2004, Mr Castro underwent emergency surgery for “sustained” intestinal bleeding in July.

For the past four months, he has been seen only in photographs and videos, even skipping a Non-Aligned Movement conference in the Cuban capital. His gaunt appearance in the last video on October 28 led many to conclude that he was too ill to take back the reins of power.

Based on the images, US officials say that Mr Castro appears to be suffering from terminal cancer of the stomach, colon or pancreas, and is unlikely to survive beyond the end of next year.

Mr Castro actually turned 80 on August 13, but his surgery forced him to put off his birthday celebration until today’s 50th anniversary of the landing of the Granma. It was the yacht that brought his guerrilla band from Mexico to launch the revolution against General Fulgencio Batista, the US-backed dictator.

When the postponement was first announced, it was assumed that Mr Castro would be well enough to appear at today’s military parade — the highlight of five days of celebrations that included an art exhibition, a concert, and a symposium called “Memory and Future: Cuba and Fidel” that was attended by fawning intellectuals from 81 countries from Venezuela to Mozambique.

Among them were Gabriel García Márquez, the Colombian author, who said that he planned to return when the Cuban leader turned 100, and Gérard Depardieu, the French actor.

Leftist Latin American and Caribbean leaders, including President Morales of Bolivia, the newly elected President Ortega of Nicaragua and President Preval of Haiti, were scheduled to attend. President Chávez of Venezuela had to stay at home for his country’s election tomorrow.

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