The Red Devils missed out on him during Sir Alex Ferguson's time in charge, with the player then plying his trade in his homeland at San Paulo.
Jose Mourinho explored signing him at the start of the month but his deal for Alexis Sanchez changed things.
That led the path clear for Tottenham who have taken full advantage to sign the forward.
Meanwhile, Neymar has hit out at PSG for failing to play Moura more during his six-year spell in Paris.
Steve Nicol says Lucas Moura to Tottenham is a good deal
“I’m sad, because he's a good friend, he's a quality player who was rarely used,” Neymar said.
“I think it's very unfair. He is my brother in football.
“I wish him the best. Whatever the destination, I hope he will score a lot and he will return to the Brazilian national team.
“He's not just a friend, he's a very good guy. Here he could have been used a lot more but I'm not the owner of the team, not the owner of Paris.
“For me, he should never have left Paris."
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