By Tom Victor Ion Tiriac enjoyed a steady tennis career, winning matches at all four Grand Slams, but his move into the world of investment has seen him amass a fortune in the billions. Tiriac, now 84, picked up some solid results on the court in the 1960s and 70s. The Romanian reached the quarter-finals of the French Open singles in 1968, losing to eventual finalist Rod Laver, and won the doubles final with compatriot Ilie Nastase in 1970. That lengthy career only brought around £200,000 in lifetime earnings, with the prize money in tennis some way shy of the numbers we’re seeing today. Since…