The 22-year old will make the move to the KCOM Stadium from the start of the 2020 campaign, with the deal seeing him remain at the club until the end of the 2023 Betfred Super League season after turning down opportunities elsewhere in Super League.
Impressive in defence, as well as possessing a strong running and kicking games, Johnstone began his career with amateur club Kells as a junior, before becoming part of the Cumbria Storm Academy. After initially joining Widnes in 2014, he would make his senior debut for home-town club Whitehaven whilst on loan in 2015.
Returning to the Vikings in 2016, Johnstone would go on to make his Super League debut later than season. A regular feature throughout the 2017 and 2018 season, the youngster also earned valuable first-team experience for the side in the Challenge Cup.
Johnstone has been a key asset for the Vikings during their Betfred Championship campaign under Kieron Purtill acting as their first choice hooker as the side aim to return to the top division.
Previous Clubs: Widnes Vikings, Whitehaven, London Broncos (loan)
Community Club: Kells
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