Meghan Markle wears royal purple for the One Young World Summit

The Duchess of Sussex wore a perfectly royal shade of purple during her latest engagement.

On Tuesday night, Meghan, 38, attended the opening ceremony of the One Young World Summit at London's Royal Albert Hall.

It was her first public appearance since a candid behind-the-scenes documentary about Meghan and husband Prince Harry aired in the UK on Sunday.

For the occasion, celebrating youth tackling issues around the world, the Duchess wore a long-sleeved purple midi dress by Aritzia, which she teamed with navy heels.

It's a dress royal fans may remember from earlier this year — Meghan wore it for her first engagement of 2019, a visit to Birkenhead in January, paired with a vibrant red coat.

The Duchess' affiliation with One Young World, a collective of global youth ambassadors, pre-dates her relationship with Prince Harry.

She attended the summit as a counsellor in Dublin in 2014 and again in Ottawa in 2016, where she met Canadian Prime Minister Justin Trudeau.

This year, the organisation partnered with The Queen's Commonwealth Trust, of which Meghan is Vice-President, to bring young leaders across the Commonwealth nations to attend the summit.

During the opening ceremony, the Duchess was announced as one of 70 counsellors to appear at the summit, along with the likes of Bob Geldof and Ellie Goulding.

Ahead of Tuesday's event, the Sussex Royal Instagram account shared photos and footage from Meghan's appearances at previous One Young World summits.

LISTEN: Find out more about Meghan's life, before and after Prince Harry, with 9Honey's royal podcast The Windsors. (Post continues.)

In one video, Meghan addresses the audience in Dublin and speaks passionately about female empowerment and impacting change, regardless of age.

"I think what scares people is that the idea of female empowerment is somehow threatening," she says.

"No, it's not! You empower the women, you're empowering the community."

She then mentions that as a child, she successfully petitioned for the wording of a TV advertisement to be changed to reflect gender equality.

"I think anything is possible, because with my small voice at 11 years old we could do it, so I can only imagine what all of you are going to be able to do," she added.

Meghan has been in the headlines this week following the release of ITV documentary Harry and Meghan: An African Journey.

The film, which gave viewers a behind-the-scenes look at the Sussexes' recent royal tour of southern Africa, featured candid interviews with the Duke and Duchess.

Meghan opened up for the first time about the storm of negative press that has surrounded her for months, admitting she was "not okay".

"Not many people have asked if I'm okay, but it's a very real thing to be going through behind the scenes," she told reporter Tom Bradby.

The former actress also recalled how she was warned the UK tabloids would "destroy" her life if she pursued a relationship with Prince Harry.

"When I first met my now-husband, my friends were really happy because I was so happy," she recalls.

"But my British friend said to me, 'I'm sure he's great, but you shouldn't do it because the British tabloids will destroy your life.'

"I very naively - I'm American, we don't have that there - [said] 'What are you talking about? That doesn't make any sense, I'm not in tabloids.' I didn't get it."

Meghan acknowledged scrutiny is an inevitable flip side of the status and wealth that comes with being in the royal family.

However, she countered that argument by saying treatment had been unreasonable.

"That [argument] completely tracks for me, if things are fair. If I've done something wrong, I'd be the first to go, 'Oh my gosh, I'm so sorry'," she explained.

"But when people are saying things that are just untrue, and they've been told they're untrue but they're still allowed to say them — I don't know anybody in the world that would feel like that's OK.

"That's different than just scrutiny. That's a different beast."