The Duke and Duchess of Sussex have paid an emotional tribute to the victims of the Christchurch terror attack today as they signed a book of condolence on behalf of the Royal Family, writing: "We are with you".

Prince Harry and a heavily-pregnant Meghan visited New Zealand House in London to pay their respects to the 50 people massacred as they prayed at two mosques on Friday.

They put their knowledge of Maori customs to good use, greeting delegates with a hongi before signing the book of condolence with the word "arohanui", which loosely translates to "much love/with deep affection".

Meghan, who cradled her bump throughout the visit, wore a pair of earrings featuring a crossed-feathers design given to her by the country's Prime Minister Jacinda Ardern.

Meghan, Duchess of Sussex, and NZ High Commissioner Sir Jerry Matepare hongi.

Both dressed solemnly in black, the pair spoke with the High Commissioner of New Zealand, Sir Jerry Mateparae, before laying floral bouquets and quietly reading other tributes left behind by members of the public.

The couple were asked by the Queen to represent the British royal family at the event, having been the last members to visit the country when they toured the South Pacific in October.

The duke and duchess met with members of staff at the High Commission to discuss their response to the atrocity.

Meghan said "we are with you", adding she was "just devastated" by the atrocity.

Harry said "it's just very sad" as he asked about their connections to Christchurch.

The Duke and Duchess of Sussex signed the Book of Condolence @NZinUK, opened following the terrorist attacks in Christchurch.

The Duke and Duchess signed the book on behalf of the @RoyalFamily — Their Royal Highnesses visited New Zealand in October 2018. pic.twitter.com/AzdsmnoS11

— Kensington Palace (@KensingtonRoyal) March 19, 2019

Mateparae said: "We are overwhelmed by the tremendous amount of support we've received from across the UK.

"Their Royal Highness's visit is reflective of this outpouring of support and it was wonderful to welcome them to New Zealand House."

The duke and duchess are among the first to sign the book of condolence, which opened to the public today.