Prince Harry has said he knew his bride-to-be Meghan Markle was "the one" from the moment they met, as the couple made their first public appearance since the announcement of their engagement.

The Prince, 33, declared that he is "thrilled" as he and the 36-year-old American actress posed for an open-air photocall in the Sunken Garden at Kensington Palace.

Their long-anticipated engagement was announced by the Prince of Wales on Monday morning with a statement saying the couple, who have been dating for 16 months, will marry in the spring next year.

A beaming Ms Markle, in a white belted coat, clutched Harry's hand with both of her hands as they posed briefly and showed off her diamond engagement ring - designed by the prince himself.

Harry revealed that he knew Ms Markle was "the one" from the first moment they met. "When did I know she was the one? Very first time we met," the prince said.