Grovelling documentaries such as this damage rather than support their cause, writes Jan Moir.
By now, we all know the Harry and Meghan drill. Their royal mission in life is to "shine a light" on hardship, to raise awareness and funds for good causes, while still being "authentic" in themselves.
And truly, they are to be commended for this.
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If they so wished, the Duke and Duchess of Sussex could slink behind the vegan silk curtains at Frogmore Cottage, they could hunker down on their Soho House velvet sofas and tell the world to go to hell, while raising baby Archie in the most private and pampered environment that only a century of British royal prerogative can provide.
However, they clearly have a sense of duty that precludes the luxury of such seclusion. Yet they want the best of both these worlds, which is where the trouble starts.
They hoped to focus on important humanitarian issues in a country still riven with gender and racial inequality, where dirt-poor black people remain trapped in townships and life expectancy rates are among the lowest in the world.
As the cameras started rolling, it was clear this could have been one of the most inspiring and amazing royal tours of all time, especially at the beginning when Meghan met young women in Nyanga township, the so-called "murder capital" of the country.
'I am here with you as a mother, as a wife, as a woman, as a woman of colour and as your sister,' she informed the small crowd that had gathered.
Her words might seem glib to first-world ears, but there is no telling how stirring they might seem to young women who could see and hear, through the Meghan prism, of a more hopeful future for themselves.
Later the duchess told documentary presenter Tom Bradby that she had added those words herself, with Harry's approval.
Bradby was given special access to the Sussexes for this hour-long documentary, and he reminded us more than once of the depth of his 20-year friendship with Prince Harry.
The two men had often talked privately, we were informed, about grief and mental health issues. Yet did we really need to hear that Tom had a few issues of his own, and had to take time off work to deal with them last year?
Bradby clearly thought this gave him a special insight into the byzantine workings of the prince's mind, who – never mind the poverty and social blight he was witnessing – was soon voicing concerns about the media spotlight on himself and his wife.
As the couple vented, Bradby crept around like a 17th-century court flunkey, tugging his flaxen forelock and holding an orange pomander to his nose at any perceived criticisms of H&M.
"This is a couple that feel themselves on a moral mission to challenge what they feel is wrong," he whispered at one point.
The shocking thing was Harry and Meghan weren't talking about luckless Africans they met who have struggled so long and so hard to overcome their ill-fated lot in life. They were talking about themselves.
On the banks of a nameless river deep in the veldt, Harry talked emotionally to the ITV cameras of his difficulties.
With the velvety embrace of the African night unfolding behind him, there he stood, this motherless son, his eyes shining like headlamps in the gathering gloom.
Every time he heard a camera click, he said, it made him think of Diana. He was still struggling, his pain was endless.
One sympathises with Harry, still seeking to apportion blame for the death of his mother 22 years later.
This is unbearably sad in itself and we have all witnessed and understood his pain. Yet there are many stages of grief, and he seems unable or unwilling to move on from the first soul-crushing phases.
If that is really how he feels about the situation, if this royal life for him is so unendurable and intolerable, then perhaps he really should desist from his duties.
Perhaps he and Meghan should opt for a quiet private life, give up the proselytising, retreat to the country. Everyone would entirely understand. Especially with a wife who complains, as Meghan did to Bradby, that no one ever asks how she is doing and that their life together is 'existing and not living'.
In conclusion, Bradby said the Sussexes hope to turn the "relentless media interest in them into a positive force for good". If so, they are going a funny way about it.
For one wonders at them visiting Angola, one of the most unfortunate countries in the world, and then using it as a backdrop to complain about their own problems.
All those wonderful people the Sussexes met across the continent, all those desperate problems they encountered, were condensed into a thin, doomed chorus that no one was listening to, while attention focused on the grandiose oratorio of their unfeigned pain, and the jolt of their first-world grievances.
Think of their plight compared to the teenage girls taking boxing lessons to fight off sexual predators who rape them with impunity. The tiny children in Angola who are still having their limbs blown off by land mines and the adults who have coped with mass killings and endless wars, not to mention a life without limbs themselves.
If you can bear witness to all of that misery and still stand in front of a camera, biting your lip or with a tear in your eye, as you complain that behind the ramparts your life is tough, then you are tone-deaf to the concerns of real people and blind as to how you are perceived.
Harry and Meghan think that people are mean to them.
They have to learn that respect has to be earned, not demanded. And that grovelling documentaries such as this damage rather than support their cause.