On Sunday the 29-year-old claimed the EBF light welterweight title at the Syndicate nightclub in Blackpool, beating Harrison in six rounds to exact revenge for a defeat at the hands of the same opponent in October.
The victory was all the more impressive as he overcame a nasty rib injury to emerge victorious. The fight had been due to take place at the Rumes nightclub in Preston on Friday December 5 but the fight was pulled the day before after concerns were raised over the security at the venue.
But confident McDermott said he had been undeterred by the earlier problems leading up to the fight and did not let his injury beat him.
He said: "The broken rib was affecting my jab but I had sheer determination that saw me through the fight and there were more than 100 fans there shouting for me. That really spurred me on and I kept jabbing him.
"I can remember him having his gumshield half out of his mouth saying 'is that all you got?' which I know meant he was frustrated."
McDermott said his training with trainer Ray Jennings and his son, British welterweight champion, Michael Jennings had given him real focus and had dramatically built up the defence and power aspect of his game.
He said he was always confident of a win over Harrison after being disappointed in his last fight in October when Harrison won with a fifth round knockout.
He said: "I had changed since the last fight and I don't think he had.
"I was also hitting the target a lot more thanks to all the work that Michael (Jennings) has been doing in the gym as I did not land as many punches before.
"He was a fantastic fighter and I think I did really well to beat him.
I don't have easy fights and that is what you expect when you are up against the best."
* For Terry's full account of his victory, plus more pictures, see this week's Longridge News