WHO IS RAÚL CASTRO? For half a century, he has laboured unobtrusively by his brother’s side, waging guerrilla warfare during the 1950s, marching into Havana in 1959 and presiding over Cuba’s Armed Forces since.

Five years younger than Fidel, Raúl has long been el comandante’s designated successor. But while Fidel is a world icon, instantly recognisable by his first name alone, Raúl remains an enigma. Cubans know almost nothing about the man, even as he has steadily extended his control to cover the security services and the Cuban Communist Party.

For much of the past 48 years, it hasn’t been a burning question: No one doubted that Fidel – and Fidel alone – made the decisions. Now that has changed. Fidel has been in hospital since July with a mystery gastrointestinal illness, and Raúl has been running the country. Suddenly everyone wants to know who the diminutive, untalkative man at Fidel’s side is – and how he will run Cuba when Fidel is gone.

Brian Latell, a former Cuba analyst for the CIA, has published his best guess at what postFidel Cuba might look like. Responding to the sudden hunger for information on Raúl, After Fidel bills itself as the “first ever biography of Raúl Castro”. In fact, its scope is much broader.

Latell has written an engaging psychological profile of the brothers and their odd relationship. He tries to explain how two such apparently different characters could combine into one of the most enduring political partnerships in history.

Apart from the fact that so little is known about him, the problem with Raúl is that the available evidence paints two radically different portraits. The Raúl that most Cubans think they know is Fidel’s hard-line enforcer, who personally supervised scores, even hundreds, of executions. He is an unyielding Marxist ideologue who championed Soviet domination of the island and vigorously fought off attempts at rapprochement with the US. He ordered the execution of his closest friend, the independent-minded General Arnaldo Ochoa. Alluding to this reputation, he once dubbed himself “Raúl the Terrible”.

But intimates paint a different picture. In contrast to Fidel, who has a prudish streak and never aknowledges relatives, Raúl is a compassionate family man who remembers birthdays and enjoys a drink.

“Unlike his brother, he has never been motivated by an ego-charged quest for fame and glory . . .” Latell writes. “He does not thrive on conflict and confrontation . . . He worries more about the economic hardships that the Cuban people endure and has been the most influential advocate in the regime for liberalising economic reforms. He is likely to be more flexible and compassionate in power.”

Fidel’s daughter Alina Fern-ández, now in Miami, calls Raúl “the practical brother”. In fact, although Fidel has never acknowledged it, his long rule has depended on Raúl’s organisational abilities. While Fidel has been the revolution’s inspiration, chief ideologue and international salesman, Raúl has held it all together.

Were it not for the economic reforms he instituted in the mid1990s, Cuba would almost certainly have followed the Soviet Union into collapse. As head of the Army, he opened up tourism and made US dollars legal tender, giving the regime enough hard currency to muddle through.

So, after Fidel, will “Raúl the Terrible” or “the practical brother” shine through? Latell’s answer is both.

“Many anecdotes about [Raúl’s] cruelty and implacability circulate among people who have known him,” he writes. “But those stories coexist with others illuminating his gentler side . . . When he succeeds his brother in power, these opposing sides of Raul’s personality will continue to be in conflict as they have since he carried out his first brutal acts.”

Latell spent three decades with the CIA, But any readers hoping for a glimpse inside the agency’s secret files will be disappointed. He draws primarily on existing accounts and interviews with Cuban defectors in Miami. During his years at the CIA, the author had to read Fidel Castro’s estimated 2,500 speeches, many lasting up to eight hours. One, in 1968, went on for a bladder-bursting 12 hours. That act of endurance alone has probably given Latell some insight into the regime, but this is not, as the cover claims, its “inside story”. Indeed, some of the best passages are a frank discussion of the limitations of US intelligence on Cuba, so often distorted by wishful thinking, a reliance on defectors and domestic politics. Sound familiar?

AFTER FIDEL by Brian Latell

Palgrave Macmillan, £8.99; 304pp £8.54 (free p&p) 0870 1608080 timesonline.co.uk/booksfirst

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