Villa academy chief Bryan Jones told the Birmingham Mail: "I first saw him playing for England when I had gone to watch one of our own players.
"You monitor things just on the off-chance a player ever becomes available.
"A week ago we learned he had turned Watford down and we were given permission to speak terms. He liked what he saw here and agreed a deal. But, as always, there is such a long way to go with a player of this age."