The early 1970s was a good time for heavyweight boxing. Indeed, it was probably the last truly great age for the sport. Flamboyant fighters contested brutal matches in exotic locations, from the Philippines to the Caribbean. The world watched open-mouthed. The marketing slogans attached to some of those fights remain instantly recognisable: who has not heard of the Rumble in the Jungle or the Thrilla in Manila? During these years boxing, and particularly American heavyweight boxing, was the most prominent and glamorous sport on the planet.