Why all missions are doomed in a land of suspicion

As an unequal contest, it compares to a football match between San Marino and Brazil. The idea that a handful of private investigators could ply their surreptitious trade in a nation as tightly controlled as Cuba was doomed from the outset. To the average, genuine tourist, Fidel Castro's island appears friendly and open. But anyone delving beyond sun, sea and salsa quickly attracts the attention of Cuba's formidable secret service.

As an unequal contest, it compares to a football match between San Marino and Brazil. The idea that a handful of private investigators could ply their surreptitious trade in a nation as tightly controlled as Cuba was doomed from the outset. To the average, genuine tourist, Fidel Castro's island appears friendly and open. But anyone delving beyond sun, sea and salsa quickly attracts the attention of Cuba's formidable secret service.

The Department of State Security, whose Spanish acronym is DSE, enjoyed 30 years of close ties with the KGB before the collapse of the Soviet Union. The organisations shared a common enemy in the CIA, and the United States agency still has a substantial covert operation in Cuba. Its activities and the economic blockade imposed by Washington for four decades, have created a siege mentality that makes all visitors to Cuba potential suspects.

At the Ministry of the Interior Museum in Havana, tourists are shown numerous well-documented CIA attempts on President Castro's life. The belligerence of the Americans towards their small neighbour helps explain why the Cuban state is hypersensitive to foreign interference.

President Castro has developed sophisticated systems for detecting irregular visitors. Loyal party members observe contacts between Cubans and foreigners, and report them to local DSE representatives. In addition, plain-clothed agents watch many of the tourist locations. There is likely to be one in the lobby of all the large hotels in Havana, looking for suspicious behaviour and liaisons between foreign clients and prostitutes, some of whom are said to work as informers.

The Castro regime has snuffed out dissent, using the vague charge of peligrosidad, literally "dangerousness", against those perceived to threaten the social or political order in Cuba. The idea of a bunch of British private eyes, posing as tourists and in the pay of an angry wife, trailing an errant husband around the last bastion of state communism, may strike the outside world as comic. But to the state security apparatus, anyone using hidden cameras and bugging devices is a prime target for arrest.

In the past decade, the number of visitors has risen dramatically, with a 70-fold increase from Britain. Despite the increased work load, surveillance is still effective - as my two encounters with the security service testify.

On one occasion, I was inspecting the remains of a Spanish colonial building in Havana when plain-clothes police arrived and detained me while they searched the rubble in case I had used it as a "drop" for passing material to a local contact. The other time, at the main tourist airport of Varadero, where I was booked to fly to Jamaica, my bags were searched minutely and a cassette of a BBC radio programme that included the voice of a particularly virulent Cuban exile in Miami was seized.

An errant visitor is left in no doubt about the attitude towards activities incompatible with the status of tourist.