MEGHAN Markle has reacted with shock after spotting an old friend in the crowd during a public walkabout in New Zealand.

The Duke and Duchess of Sussex - accompanied by Prime Minister Jacinda Ardern - had just wrapped up their public walkabout on Tuesday and were about to leave the Viaduct Harbour in Auckland when the former Suits star noticed Hannah Sergel, 20, standing amid thousands of fans.

Meghan's jaw dropped and she doubled back, embracing Hannah whom she'd used to follow on Instagram before she deactivated her accounts.

"She said 'thank you for getting in touch,' and then she gave me a hug and said she would read my letter that I gave her," Hannah told New Zealand's 1 NEWS.

"I was friends with her on Instagram before she had to deactivate her account. We used to have conversations and stuff on there. She would tell me to do well at university and encourage me to be myself."

Hannah added that it "means the world" to her that Meghan had recognised her.

"I am so shaky and flustered. When I first saw her, I cried," she told the outlet afterwards.

To top it off, Hannah posted on Twitter a short time later that the prime minister had "DM'd" (direct messaged) her with a photo of the encounter.

She also admitted that Ms Ardern had to comfort her because she was "such a mess" after meeting Meghan.

The prime minister has also clearly bonded with Meghan during their short time together, offering up gushing praise for the pregnant royal at a formal reception in Auckland last night.

Ms Ardern told Meghan she thought she was "incredible" for the way she'd handled the exhausting tour, which started more than two weeks ago.

The Duke and Duchess of Sussex will finally wrap up their marathon 16-day royal tour today, which has seen them undertake activities across Australia, Tonga, Fiji and New Zealand.

But before they fly back to London, the couple will spend the day in Rotorua, where they'll watch a formal powhiri - welcome ceremony - and visit a nature park to learn about a breeding program.