LONDON (Reuters) - Britain s Prince Harry, who announced earlier on Monday he was engaged to his American girlfriend Meghan Markle, said they were both thrilled as they posed for their first picture together after the announcement.  Thrilled. Over the moon,  Harry said when asked how he felt. When asked by reporters when he knew she was the one, he said:  The very first time we met.  Asked if his proposal was romantic, Harry replied:  Of course it was,  before leaving with an arm around his fiancee who showed off her diamond engagement ring to photographers. 