ATHLETES who dominate the competition are impressive to watch, but sport is at its most entertaining when it features an iconic rivalry, especially between people with wildly contrasting personalities: Ronaldo v. Messi, Frazier v. Ali, McEnroe v. Borg — rivalry that challenged these sportsmen to reach greater heights, bringing out the best in each other and, on occasions, the worst.

The rivalry and subsequent friendship of one such pairing, but a female one, is the subject of Chris and Martina: The final set (Netflix, available now), a documentary exploring the intertwined careers of the former world number-one tennis stars Chris Evert and Martina Navratilova. Evert, the all-American sweetheart, and Czech Navratilova, the defector from a communist regime — both were competitive to the exclusion of all else, “cold-hearted pursuers of greatness”, who battled it out on the court in the late ’70s and throughout the ’80s.

Their relationship ebbed and flowed from closeness to calculated distance, but deepened in their later years as they turned to one another for support with individual cancer diagnoses. Some of that struggle is documented here, including the punishing wait for scan results and the debilitating impact of chemotherapy.

The story is brave and brutal, with no soothing veneer to preserve the awkwardness of its subjects’ having to relive some unflattering memories. This makes it uncomfortably real, but all the more powerful for it. Here are two women who have lived long enough to be unafraid of honesty and have no need of a puff piece. This story of phenomenal athletes and truly great women is a must-watch.

Alexander Armstrong Across America (Channel 5, 27 June) is a new four-part travel series. Armstrong is immensely likeable, and the clash of his terribly well-bred Englishness with brash American culture is amusingly jarring. He also tells a decent yarn; and there is plenty to tell about the world’s richest nation, especially as it celebrates the 250th anniversary of where the United States began.

This episode explores Pennsylvania, starting with Philadelphia, the city of brotherly love, named with holy hope by the Quaker William Penn. Besides taking in a light spot of history, Armstrong consumes a far less light Philly Cheese Steak sandwich, which goes a long way to explain the obesity problem in the US.

Also discussed are the city’s critical epidemic of drug addiction and the heroic charitable efforts being made to ease that terrible suffering. It is a city — and a nation — of bewildering contrasts: a dream of wealth and freedom for some, a nightmare for others. I look forward to the rest of the series.