The Duchess of Sussex made a surprise appearance at the London Stadium, when she joined her husband for a Major League Baseball match between Boston Red Sox and the New York Yankees.
The royal couple attended the first of a two-game series, which is being held to promote American baseball in the UK.
Before the match they were presented with a Yankees shirt and a Red Sox baby bodysuit for their son Archie.
It is the first regular-season, MLB game to be played in Europe.
Organisers want to grow the sport internationally.
Although this is not the first time MLB matches have been played outside the US or Canada, MLB vice-president of international strategy Charlie Hill said: "We want more people aware, playing and watching our sport."
MLB is also putting on a three-day festival in east London at which fans can immerse themselves in American culture, food and live music.
Prince Harry and Meghan, Duchess of Sussex were joined by members of the Invictus Games Foundation on the field for a ceremonial first pitch.