The Toksport Skoda driver came down with a stomach bug on the eve of the Safari Rally that marked the start of his WRC2 campaign.
The illness left Greensmith severely sapped of energy ahead of the toughest rally on the WRC calendar. However, the 27-year-old refused to quit and relied heavily on hydration tablets to get him through the rally which resulted in a faultless run to victory.
Greensmith set the pace from the onset to move into a comfortable lead of more than three minutes at the end of Friday.
Once out in front, he managed his pace after main rival Oliver Solberg dropped almost four minutes following punctures on stages two and three. Greensmith eventually took the victory from Solberg, who also felt the effects of a fever, by 1m23.1s.
"I don't know what I'm more proud of, not shitting myself on Friday or actually winning the rally, it has been a long weekend but I'm very happy," Greensmith joked at the finish.
"It's a brilliant way to start the season, the car has been impeccable.
"There was no point that I thought I was going to [give up on the rally due to illness] because I knew I couldn't from my own personal thing.
Source: Autosport