HAVANA - President Fidel Castro turns 70 tomorrow after more than half a life in power, firmly at the helm. Castro is burlier and greyer than he was when his rebel army took power on January 1st, 1959. With Cuba's economy dealt a near fatal blow by the collapse of communism in the former Soviet bloc, he has been forced into some ideological compromises in recent years, steering Cuba through cautious economic liberalisation.