Cornish took another important step towards his ultimate dream of contesting a world title when he destroyed Hungarian champion Zoltan Csala at the Bellahouston Leisure Centre in Glasgow at the weekend.
The 28-year-old Highlander stopped Csala, 33, after 47 seconds of the fourth round when he rocked his opponent with a big right before moving in for the kill.
Having been set up by Cornish’s jab, Csala was open to a right cross and he only just managed to stay on his feet when it connected.
But when Cornish followed up with a flurry of blows, driving Csala into the corner, referee Terry O’Connor wisely waved it over.
Cornish’s 21st straight win earned him the vacant IBO International championship and the distinction of becoming the first Scot to hold a heavyweight title of any significance.
But McDermott, 34, will be a much tougher proposition, despite two years out of the ring, and Cornish’s special adviser Kellie Maloney said: “I think it will be one hell of a fight.
“When John heard I was coming back to boxing he was straight on the phone asking to box again and he has to be respected. He was the original choice of opponent for this fight but he didn’t feel he could get ready in time.
“Gary roared against Csala and gave the fans what they wanted to see but this will be his toughest test to date and it will prove if he’s got anything.”
Cornish said: “I’m proud of my achievement and overwhelmed at becoming part of ring history.
“I felt I made a statement and people should take notice of me as Csala is ranked 50 places above me in the world and had never been stopped, yet I made him look average.
“We knew Csala would try to come forward swinging and it was my job to keep him at range. I stepped off a bit when I should have been straight on top of him but that’s all part of the learning process and I will be back in the gym on Monday fixing the mistakes.
“McDermott will be dangerous because he’s a good fighter who has been on the wrong end of some dodgy decisions.”
McDermott praised Cornish’s performance, but he insisted: “I think I have more than I need to handle Gary.
“He’s a good fighter and beat a tough and dangerous opponent who was hard work as he was covering up more than fighting.
“But it is all about experience and Gary has not boxed in my class.
“I have boxed at the top level and I guarantee that six of my eight defeats were bad decisions, including the one against Tyson Fury.
“I’ve also sparred the best, including Wladimir Klitschko.”
Interestingly, McDermott works for a company specialising in the preservation of national monuments, including Nelson’s Column and Big Ben, but he may find Cornish an even more immovable object.