The veteran presenter has been reunited with his ex-BBC colleague Susanna Reid as he makes his return to breakfast television on Monday, amid a lenthy battle against prostate cancer.
Tunbull, 64, had not presented on live TV since he quit BBC Breakfast in 2016 following his cancer diagnosis, and had not worked with Reid since 2014 when she made the move to ITV.
And Turnbull annouced that he was "thrilled" to be working with Reid again, and promised thre would be "quite a few differences" between him and Morgan, adding that he doesn't "have such strong opinions as Piers has and [doesn't] voice them as much as he likes to."
But his appearance left fans questioning what had happened to regular host Morgan, and viewers wondered when he would be making his return to the ITV morning flagship show.
It was announced towards the end of last year that Morgan would be having a short break from presenting the show this week.
Morgan is currently in the United States and shared a photo on Twitter of him and cricketer Shane Warne having a drink together in Los Angeles.
— Piers Morgan (@piersmorgan)February 24, 2020
Turnbull is stepping into Morgan's shoes for just three days as the regular host has a short holiday.
Turnbull will be presenting on Monday, Tuesday and Wednesday this week.
Speaking about his return to the show, Turnbull said: "We didn’t work together long enough and we got on so well. I was so sad when she left at short notice. So for her to ask me to sit alongside her is very exciting.
"I’m in two minds about the early mornings. On one hand, it’s great to be back doing live television. The other part of me thinks: ‘What on earth am I doing? Having sworn never to do breakfast television again!
"But here I am doing it and it’s only in the short term."
Turnbull appeared on the Good Morning sofa in November last year to discuss his Channel 4 documentary Staying Alive, which followed the presenter as he underwent cancer treatment.
The presnter's cancer has spread to his bones, but said he still has a "fair old time to live".