Johnston was born in Johannesburg, South Africa to Australian parents; he returned home to Australia with his family as a small child.
[3] At the age of six, Johnston contracted osteomyelitis and came close to losing his leg and would have done if not for the expertise of an American specialist who was touring and lecturing in Australia at the time.
[5] Encouraged by his father Colin, who had trialled at Preston North End and Dundee United,[6] aged 15, he wrote to several English clubs, with Middlesbrough replying.
[7] In his first match as a trialist, at half time and 3–0 down he was told by then manager Jack Charlton “you are the worst footballer I have ever seen in my life.
[12] Johnston scored his first goal for Liverpool on 8 December 1981 against Arsenal at Anfield, during a League Cup fourth round replay.
[12] He worked under three managers – Bob Paisley, Joe Fagan and Kenny Dalglish – and, when picked, predominantly played on the right side of midfield.
[2] In 1988, he was a frequent substitute and occasional starter as Liverpool again won the League title and reached the FA Cup final, aiming to complete a second "double".
After 270 appearances and 40 goals and just days before the 1988 FA Cup Final at Wembley against Wimbledon, Johnston announced his premature retirement from football to manager Kenny Dalglish.
However, Johnston then filmed German legends Franz Beckenbauer, Karl-Heinz Rummenigge and Paul Breitner using the boots in snowy conditions, which led to Adidas agreeing to the proposal.
[21] Johnston also invented the Traxion sole for football boots and the software program the 'Butler,' a device that shows what has been removed from minibars in hotel bedrooms.
[22] Johnston invested heavily in a football school idea for inner city children but failed to win expected business backing and went bankrupt.
[23] Johnston was the creator of TV game show The Main Event, which aired for two years in the early 1990s in Australia and a season in the UK in 1993.
[25] On 18 June 2006, Johnston made an appearance as a guest on The Footy Show World Cup Spectacular in Germany revealing information on his career.
During the 2010 FIFA World Cup, Johnston wrote a 12-page letter to FIFA president, Sepp Blatter, in which he collected all criticism by players and coaches of the controversial Adidas-produced Jabulani ball, risking his reputation, and expecting to be blacklisted by the conservative governing body as a result of this letter.