In 1979, Johnstone turned professional and has spent his career playing mainly on the Southern African Tour and the European Tour. He won six times in Europe and finished a career best seventh on the European Tour Order of Merit in 1992. His most prestigious win came at the 1992 British PGA Championship. He won seventeen times on the Southern African Tour and topped the tour's Order of Merit in 1988–89 and 1993–94. He has represented Zimbabwe in international competition many times.
Johnstone is noted for his excellent short game and topped the European Tour's short game statistics in 1998, 1999 and 2000.
Broadcasting career
Johnstone currently works for Sky Sports as golf commentator. He was also a presenter for a television series called Bush Hacking. Three seasons were produced which were filmed in the Kruger Park and Shamwari in South Africa. The two minute episodes were broadcast as fillers during live golf coverage on Sky Sports and also broadcast on SuperGolf on SuperSport.
In 2004, Johnstone was diagnosed with multiple sclerosis, possibly ending his playing career. With a revolutionary drug treatment, he appears to have put his MS in remission.[3]