The Yankees are playing two regular-season games against their arch rivals Boston in the English capital and the opening night was a smash hit.
"That's something they can never take from me", he said.
Boston lost both games in London and trail NY by 11 games in the AL East standings.
Tanaka got two outs as he failed to finish the first inning for the first time in 149 major league starts.
NY regained the lead on Brett Gardner's two-run home run in the third inning.
For the first time in the history of the Red Sox-Yankees' famous rivalry, both starting pitchers - Boston's Rick Porcello and New York's Masahiro Tanaka - were replaced in the first inning in a game that ranked as the second highest scoring clash between the clubs. Xander Bogaerts, J.D. Martinez and Christian Vazquez became the first trio of Boston batters in four decades to hit home runs in the first inning, banging and mashing to a 4-0 lead against Stephen Tarpley, who was making his first big league start.
Some 30 runs were scored, to make it the game with the most runs since Boston beat the Baltimore Orioles 19-12 past year.
All-Star second baseman DJ LeMahieu led off with a single and scored on first baseman Luke Voit's RBI double. The second match will take place on Sunday.
With Red Sox starter Eduardo Rodriguez' pitch count at 108 after five innings the lefty opened the sixth against the left-handed hitting Gregorius leading off. Gregorius was 1-for-2 against Rodriguez which hiked the career average against Rodriguez to.324 (11-for-34). I'm glad to be coming back next year.
New Yankee Edwin Encarnacion then doubled to score Gregorius from second.
The royal's baseball outing comes just over nine years since he threw the first pitch for hosts New York Mets against the Minnesota Twins on Britain's Armed Forces Day.
In recent days, we also learned that Meghan had her engagement ring, designed for her especially by Prince Harry himself and featuring two diamonds from his late mother Princess Diana's collection, updated as an anniversary gift from her husband.
Boston played well for most of the game and led 4-2 going into the seventh inning.