Cape Town - Niki Lauda has revealed that such was the discontent between Lewis Hamilton and Nico Rosberg that the former team-mates wouldn't even say hello in the morning.
With Mercedes dominating Formula 1 from 2014 to 2016, the battle for the World title was an intra-team tussle that often grew heated.
Both Hamilton and Rosberg refused to give an inch, which resulted in collisions most notably at the 2016 Spanish GP.
"We had huge competition within the team which was sometimes too much," Lauda, Mercedes non-executive chairman, said in an interview with Graham Bensinger on YouTube.
"We put some regulations in, we told them - especially in Barcelona when the pushed each other off the track - we said this was unacceptable for Mercedes, we have to win, one of you guys has to win, you cannot push each other off.
"We had some rules put in, they understood. You are not allowed to [do that] and you have to pay a penalty if you do it again or we will think of releasing you from your contract, because we are team players here and the team cannot destroy each other. This was the thing.
"Toto [Wolff] came up with some good rules and we had peace again. We fought hard and the accidents got reduced between them."
But while the on-track collisions became a thing of the past, the relationship between the team-mates never recovered.
"They had no relation, which is always bad," Lauda explained. "They were so bad that they didn't even say hello in the morning.
"I don't expect them to have breakfast together if they don't like each other, you don't expect them to sit down and have breakfast, but the relationship was really bad. It affected Lewis mainly and Nico, so it was fine but not easy.
"Lewis got upset that even sometimes he lost because they were playing tricks on each other which was bad for the team. You both want to go forward, not only one, so they played all the tricks they can do. For the team it was pretty tiring."