"I'm buzzing to be here and I'm excited to get going," Johnstone told club media. He also revealed that former Celtic and England goalkeeper Joe Hart had personally called him to endorse the move.

"I didn't need convincing by anyone, but Joe Hart rang me the other day just to reiterate what a place this is, what a great group of lads and how the fans are unbelievable," he said.

Johnstone highlighted the scale of the club and the culture of ambition that attracted him. "The pressure to win, which is what I like — pressure to win, pressure to perform and we all want to win trophies," he added.

He also spoke warmly about the prospect of working alongside Sinisalo. "I think everyone knows the goalie groups are a tight-knit group. We work closely together every day and hopefully I can help Vil and he can help me, and we push each other and we support each other along with the other goalies and the goalie coaches," he said.

Filling a gap left by Schmeichel's retirement

The signing addresses a void created when Kasper Schmeichel — who had been Celtic's first-choice keeper since the summer of 2024 — retired in February due to a shoulder injury, having played his final match earlier that month.

Manager Martin O'Neill welcomed the addition, saying Johnstone is "a quality keeper with excellent experience at the highest level" and predicting he would prove "a very good addition to our goalkeeping team."