Born in Viewpark, Lanarkshire in 1944, Johnstone's talent was evident from an early age. When he was 13 he was approached by Manchester United while playing for the Boys' Guild in Viewpark, but Celtic Park's chief scout John Higgins stepped in and offered Johnstone a ballboy job at Parkhead. He signed for Celtic soon after and was farmed out to Celtic Blantyre for a couple of years where his skills made an instant impression.

Johnstone made his first team debut in 1963 and quicly became a favourite amongst the fans for his prowess on the wing. He went on to become one of the world's greatest footballers with a rare ability to take on players and open up defences. If his talent had not been so exceptional, it is doubtful that manager Jock Stein would have put up with his hotheaded temperament for very long.

Unfortunately Johnstone's flair was under-exploited by the national side. He was never given the chance to prove his full potential at international level, winning a mere 23 full caps for Scotland during his playing career.

Johnstone scored more than 100 goals for Celtic, and after leaving in 1975, he had spells with San Jose Earthquakes, Sheffield United, Dundee Shelbourne and Elgin City before being reinstated as a junior with Blantyre Celtic.