Harry was highlighting the ongoing threat of the munitions in Angola, the same nation Diana visited in 1997 to urge the world to ban the weapons.

Near the south-eastern town of Dirico, the duke walked into an area that was once an artillery base for anti-government forces who had mined the position in 2000 before retreating.

The duke walked through an area of the site, looking at the marked off areas which could potentially contain landmines.

An anti-personnel mine had been discovered earlier and Harry was asked to set off a controlled explosion to safely destroy the decades-old weapon.

Praising the work of landmine clearance charity the Halo Trust, the duke called landmines an "unhealed scar of war", adding: "By clearing the landmines we can help this community find peace, and with peace comes opportunity.

"Additionally, we can protect the diverse and unique wildlife that relies on the beautiful Kuito river that I slept beside last night.

"That river and those wildlife are your natural assets and, if looked after, will bring you unlimited opportunities in the conservation-led economy."

The duke called for an international effort to clear remaining landmines from the Okavango watershed in the Angolan highlands - a legacy of the country's civil war that ended in 2002.

"It is fitting that this project starts in Dirico, at the convergence of the two rivers that flow from Angola's islands down to the Okavango Delta," Harry said.

"These two rivers provide water and life to over a million people downstream and an essential and incredibly delicate habitat for an abundance of wildlife.

"Just as these rivers extend for miles, so must this project extend far beyond Dirico. Outside the national parks, large parts of this crucial watershed also need to be cleared of landmines.

"Clearing the full watershed will take an international effort. Everyone who recognises the priceless importance of safeguarding Africa's most intact natural landscape should commit fully to this mission."

The dusty scrubland was marked with red warning signs showing the skull and crossbones, with the Portuguese words "Perigo Minas!" and the English translation below - "Danger mines".

Jose Antonio, of the Halo Trust, took Harry on to the site where his staff have been working since August to make safe, and said he hopes they can complete their painstaking clearance by the end of October.

Like all those visiting the trust's site, Harry had been given a safety briefing and told not stray off the cleared lanes, touch anything or run.

He watched as a mine clearance worker used a metal detector to search for the mostly anti-personnel mines buried in the ground.

If one is discovered, staff are trained to move back and carefully remove the soil as they move forward until they reach the munition.

More than two decades ago, Princess Diana said the issue of landmines in Angola was "a vital but largely neglected issue".

She walked the minefields 22 years ago.

Here is how The Telegraph covered the visit in its edition on Jan 16, 1997, the day after she walked the minefields.

Last week their harvest there was 50 mines. Asked about reported differences with ministers, she did well to say: "It is a distraction we don't need."

Having followed most of her movements out here, I can testify that the way she has set about her mission of support for the Red Cross campaign against mines has been irreproachable.

The whole scene in this ravaged country is calculated,to catch her heart. She has been absorbed by some of her encounters with victims of mines.

Her first call in Huambo yesterday was to the local hospital where she met Rosaline Domingo, 16.  A mine had destroyed her right leg and her baby. In this region that is a commonplace tale.

She was also absorbed by what the smart ex-soldiers of Halo Trust told her about their work. They had gathered a pile of unexploded ordnance gathered for inspection. Later she detonated another pile.

A pity, some thought, that Lt Col Colin Mitchell — "Mad Mitch" of the Argyll and Sutherland Highlanders — had not lived to see this recognition of Halo Trust's work on mines in the world. He founded it.

What makes the mine clearers' work so difficult in this region are the fragments of war that litter the surrounding fields.

For every 20 pieces of metal that set the mine detectors humming, only one may be a mine. Like the Princess, the Red Cross leaders who are out here with her can see no valid reason for government anger.

As one of the world's leading humanitarian organisations, International Red Cross believes that A/P mines transgress a convention of war in that they cause human suffering wholly disproportionate to their military value.

So they are calling for an immediate global ban on them by all countries.

By undertaking this position on behalf of such a powerful international organisation, the Princess has unmistakably signalled her support for this.

The British Government, on the other hand, opposes an immediate ban. It does not think it would be workable. So it seeks to reach foggy compromises by which, some think, it simply compromises itself.

So there are important differences,that cannot be glossed over but, made aware of the Government's position before she came out to Angola, the Princess has played it by the book.

Accompanied most of the time by our ambassador in Angola, she has said and done nothing to trouble him or the Foreign Office.

Her visit, inevitably, attracted enormous attention from the news media; but it was not seriously controversial until someone in London made it so.

In the light of how the Princess has handled this serious humanitarian issue, those of us who have been with her reckon she deserved better.