Despite interest from Liverpool the Sporting Lisbon star agreed to the switch yesterday, after returning from a disappointing early World Cup exit with Portugal.
Viana didn't take part in any of Portugal's games, but is expected to have a vital part to play in their European Championship campaign in two years time.
"We have signed Hugo for 12 million dollars and we are delighted to have got him," confirmed Freddy Shepherd to the Evening Chronicle.
"The general concensus of opinion is that he is the best young player in the world at the moment.
"He is a left-sided midfielder and just the player Bobby Robson wants to spearhead our Champions' League bid for next season.
" But, to tell the truth, we had a few scary moments. Sporting Lisbon had already agreed a fee with Celta Vigo and then Liverpool actually moved in yesterday.
"However, Douglas and myself were determined to get our man and we have kept the Sporting people up through the night."