TOM BOWER: Nigeria may have greeted Harry and Meghan with adulation... but cynics might think there's another motive behind this bout of self-promotion

Dressed like a Hollywood A-lister at the Oscars, Meghan Markle's perma-smile throughout her three-day 'royal tour' in Nigeria said it all: 'I've won.'

As she flies back to Los Angeles today, with a stop-over at Heathrow, she can reflect on having established herself as a popular British royal in Nigeria. I doubt she can quite believe it.

In a brilliantly choreographed succession of events, the Duchess of Sussex could luxuriate in the sort of attention for which every Californian film star yearns.

Tirelessly, she smiled, chit-chatted, clapped and posed for selfies with those she believes, thanks to a genealogy test, to be descended from her own ancestral roots.

It's a welcome boost both for Brand Sussex and in particular for Meghan who, until she touched down in Lagos, was rather struggling to ditch her image as a less than successful podcaster and fledgling jam-maker.

Now, dressed in a whirling array of expensive and, on occasion, flesh-baring dresses, she appeared positively presidential, a thousand miles from the staid, reassuring royal visitor from London that Nigerians might once have expected.

Prince Harry and Meghan visit the State Governor House in Lagos on May 12

Tirelessly, Meghan smiled, chit-chatted, clapped and posed for selfies

Sceptics might wonder whether this latest leg of Brand Sussex's hectic campaign of self-promotion revolved around not only their own commercial interests, but at the British Royal Family.

The duchess never let anyone forget just why her visit to Nigeria was special.

Her mother's forefather, she says, was a Nigerian taken as a slave to America, and a DNA test had concluded she was 43 per cent Nigerian. This, she told her hosts, is 'my country'.

Of course, she understands that it is marriage to Prince Harry that has propelled an actress in a cable TV show, who was relatively unknown in the UK, to global fame. And rarely has any wife shown so much public adoration for a husband than Meghan over the last three days.

Breathlessly, she expressed her love for him, for her children - Prince Archie, five, and Princess Lilibet, two - and her unstinting love for her audience.

But hers was a starring role. Indeed, the 42-year-old's unwavering self-confidence was to the fore as, with genuine aplomb, she delivered her carefully crafted script. 

Amid all that relentless promotion of the Sussex brand and the Invictus Games, there was scant mention of Nigeria's status as an important member of the Commonwealth - an organisation of 54 countries so cherished by the late Queen Elizabeth.

Just six years ago, the Queen appointed Meghan as an ambassador to the Commonwealth. Later, she was elevated by Her Majesty to be vice president of the Commonwealth Trust.

At the time, few could have imagined that Meghan and Harry would soon be denouncing members of their own family as racist in a television interview with Oprah Winfrey.

I'm not surprised that the Sussexes now seem to have retreated from their outrageous suggestion, made to Oprah, that Buckingham Palace had decided - before their son Archie was even born - to deny him a title and security protection because he is mixed race.

The Duke and Duchess of Sussex attend a polo fundraiser in Lagos on May 12

Meghan received much adulation from crowds on the visit to Nigeria

For all the adulation they've received from crowds in Nigeria, I find it hard to shake off a sense of anger about their attacks on the Royal Family on television and in Spare, Harry's best-selling memoir. The Sussexes seem oblivious to the enormous damage they have caused.

Meanwhile, King Charles is emerging slowly from his cancer treatment while  the Princess of Wales continues to fight her own battle with the disease.

As the Sussexes enjoy VIP luxury in Heathrow's aptly named Windsor Lounge awaiting their onward flight to Los Angeles - no doubt scrolling through the glowing reports of their trip - perhaps they could ask themselves this: was it really too much, while on their visit to Nigeria, to send public good wishes to their stricken relatives?

I wonder whether, more privately, they might have the honesty to acknowledge that all this fame and status has its roots in the very institution that they have chosen to attack.

I doubt it.

Curbing this graceless sabotage is King Charles's responsibility.

Only by stripping the Sussexes of their titles – their most obvious connection with true royalty – can the charade be terminated.

And for the sake of the Royal Family, Charles should end the farce of Harry using the Commonwealth as a prop for Brand Sussex.