Earlier this year, the pair had got the call about potentially reviving the soap opera, which aired its final episode on 4 November 2003.
“I couldn’t persuade him to do it,” Johnston said.
“He wouldn’t do it, would he?”
“Not at first, no,” agreed Tomlinson, who played Bobby between 1982 and 1988.
“And then I thought, because we’ve both [been granted] freedom of the city of Liverpool, I thought we’ve got a duty really to promote Liverpool, get more young actors and people into the business working.
“I’m delighted I decided to do it.”
While the storyline for the special episode was a close-kept secret, they knew it would be a crossover with Hollyoaks to mark the soap’s 30th anniversary.
Both were conceived by Grange Hill creator Sir Philip Redmond, with Brookside later paving the way for the creation of Chester-based Hollyoaks.
