Answer
Inter Milan made Christian Vieri the world's most expensive player in 1999 by paying Lazio a record-breaking transfer fee of £32 million. Vieri had established himself as a prolific goalscorer at Lazio, and Inter Milan saw him as the key to their quest for domestic and European success. The transfer made Vieri the most expensive player in the world at the time, surpassing the previous record held by Ronaldo.