But they were both all smiles when they bumped into each other on the fairway at Wentworth Golf Club in Surrey.
Watch: Piers Morgan rails against 'cancel culture' on 60 Minutes Australia
“Planning our new show... ‘Good Morning BBC Breakfast Britain’,” he quipped, adding the hashtag "#DreamTeam".
"If you pass your medical it could happen," Walker tweeted back.
Walker shared the same snap and included a video clip of Morgan taking a shot.
“Can’t believe it... turn up at Wentworth and guess who is in the group in front???? Yep... @piersmorgan," he wrote.
“And... crucially... he delivered the goods #Shanksville."
Fans were thoroughly amused by the unexpected selfie.
“Omg a picture I thought I’d never see,” said one person on Instagram, while another wrote: “Dan Walker and Piers Morgan together. Never thought I would see the day.”
“Awww I love your little bromance! You love each other really,” said one fan, adding: “Enjoy your day fellas. Let us know who has the better round!”
Plenty of people said they would love to see the rivals work together on a breakfast show.
“That would be interesting morning television,” said one, while others joked that they would happily be late to work if it meant seeing Morgan and Walker sharing the screen.
The presenters have often criticised each other on Twitter over the years and continued to antagonise each other after Morgan's infamous walk-out of the GMB studio.
Walker pretended to have stormed out over a BBC weather report, while Morgan shot back: "I'm surprised BBC bosses didn't storm in and drag you off set after yesterday's ratings came in."
As he left his job at ITV, Morgan took a final swipe at BBC Breakfast, tweeting: “I had one goal when I joined GMB – beat BBC Breakfast in the ratings.
"On my last day, we did it. That was down to the hard work and dedication of the whole team. They don’t all agree with me, some don’t even like me, but we were a team… and we won.”
When Walker heard the news of Morgan's exit, he tweeted: "Sorry to hear the news about your departure from GMB @piersmorgan. If you’d like to come on the UK’s number 1 breakfast show to talk about it... we could make some space for you in the morning."
However, Walker has also spoken up for Morgan following his GMB exit, recently saying: “He likes to throw a few insults around, but underneath all the froth I think there is a decent bloke fighting to get out."
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