Johnston, born on February 26, 1922, at Beeac, some one hundred miles out of Melbourne, took to cricket from his earliest days, when he and his elder brother, Allan, played nearly all the year round in the backyard of the farm owned by their father. In the dairy-farming area in which the Johnston family lived, the local Beeac team, which competed in the Colac District Association, occasionally found difficulty in fielding a full side, and, when only twelve, William and his brother were asked to make up the team. The invitation came through Johnston's teacher at the Ondit State School which the brothers attended. When, in their first match, a draw became inevitable, the Beeac captain called for William to take the last over, and the little lad went home proudly with an analysis of one wicket for no runs. Next year the Johnston brothers were the main bowlers of Beeac, for whom they continued to play after moving to Colac High School, where William became captain of the cricket and football teams and head prefect. On leaving school when sixteen, William found employment for a time in Colac, but in 1939 he decided to follow Allan, who had gone to Melbourne to work. When the cricket season started three months later, William played for Richmond C.C. Third XI and in his first match took six wickets for 16. After five games in which he dismissed over twenty batsmen he was promoted to the Second XI, and for the last game of the season rose to the first team. The following season, when nineteen, he was invited to play for Victoria against Queensland, but the disaster of Pearl Harbour caused cricket to be abandoned.
Before the war Johnston bowled only slow-medium, but one day when practising at the nets he slipped in a fast ball to J. S. Ryder, the former Test batsman. This so impressed Ryder that he began a personal campaign to induce Johnston to alter his style of bowling. Johnston confesses he was not very happy about the idea at the time, but in the nets he tried hard to develop the faster bowling. After a wait of nearly four years, during which he served in the R.A.A.F., Johnston was again picked for Victoria, and he was considerably surprised when his captain asked him to open the attack. No doubt Ryder, a Victoria selector and still of the opinion that Johnston's talents would best be used in fast bowling, was instrumental in the move. For a long time Johnston began the bowling believing that he would be called upon only for a few overs before being allowed to change to his more natural slows, but when opportunities for slow bowling became still less frequent he thought seriously of giving up the game. Even though he dismissed Washbrook in the first over for Victoria against Hammond's 1946-47 team, he could not persuade himself that he was utilising his skill to the best advantage, but Bradman took him aside during a State match and settled his doubts. Bradman told Johnston that the selectors thought highly of his possibilities as a medium-fast bowler to back up the shock tactics of Lindwall and Miller, and advised him to concentrate on improving his accuracy and control as the best means of getting into the Test team. No man could have received greater encouragement at such a critical time in his cricketing life, and Johnston practised assiduously to fit himself for his chance. For Victoria in the third match of the Indian tour he jumped into prominence by taking the first three wickets for no runs, and he played in four Tests, heading the averages with 16 wickets for 11.37 runs each. He took five for 48 in the second Test and six for 77 in the third. Success in State games helped to ensure his choice for England.
In both Test and county games during the 1948 tour Johnston was called upon to do most of the bowling. He sent down nearly 200 overs more than anyone else and only he took over 100 wickets. Included in his best performances were ten for 40 in his second match in England, against Yorkshire at Bradford, where he bowled slow on a wet pitch, eight for 68 against Somerset, eleven for 117 v. Hampshire, and nine for 183 in the First Test, when his five for 36 hastened England's first innings failure. At one period it seemed that Johnston was in danger of being over-bowled, but the signals were read just In time and subsequently he was used more sparingly. As the tour progressed Johnston perfected his control and became the most improved bowler on the side.
Johnston, taking a ten-pace approach to the wicket and dipping his head in curious fashion before gearing himself up for delivery, found that the English pitches and heavy atmosphere suited his fast-medium bowling which, like nearly all Australians of his type, he delivers over the wicket because of the increased chances of leg-before decisions and of the ball running away from the batsmen to the slips. His stock ball swings in to the right-hander, but he mixes this with one which goes the other way. Because of the late swing in flight the batsman's difficulty in deciding which way the ball would move brought Johnston the majority of his wickets in England. Johnston cannot work up speed comparable with Lindwall or Miller, and before he bowls his right ankle has to be bound tightly in order to check the jarring it receives in his awkward delivery. Johnston has not discarded his slows and when he chooses can still spin a great deal, but he realises the danger of trying to follow two types of bowling at the same time. It is a fact, though, that many Australians still believe he would do even better as a slow bowler.
Although always a keen student of the game, Johnston did not see a State match till he played in one, and he watched only one Test before being picked for Australia against India. During the early days of his first-class career he would return home from the match and, in the light of his latest experiences on the field, study again articles by Bradman, Oldfield and Mailey in a book given him years before by his school teacher in Ondit. He is also appreciative of the great help given him by the Richmond club.
Johnston enjoys unorthodox left-hand hitting and he fields far better than the English public were given to believe before the start of the 1948 tour. Besides cricket, Johnston has gained considerable notice as a baseball player. He won the world's junior championship for throwing a distance of 125 yards, and he broke the Australian baseball long distance record with a 132 yards throw in September 1945. During his 1948 tour Johnston paid a visit to the grave of his brother Allan, who crashed in Ireland on R.A.A.F. service. He is unmarried.