Williams' George Russell was fit enough to drive on Friday after becoming unwell in the run-up to the Abu Dhabi Grand Prix weekend.
Russel's condition had his team scrambling for a potential replacement in the event that the 21-year-old would not be up to the task of driving.
Williams reserve driver Nicholas Latifi could not be drafted in because the Canadian is not yet in possession of a superlicence, not to mention the fact that Latifi is also committed to this weekend's F2 finale in Abu Dhabi.
Esteban Ocon - contracted to Mercedes, Williams' engine partner, until next week - was seen as the next best option, but the Frenchman lanky stature didn't fit properly into Russell's FW42.
Deputy team principal Claire Williams then recruited its former driver Sergey Sirotkin to remain on standby on Friday morning, but ultimately Russell took to the track and gave his team the thumbs.
Russell was reluctant however to go into detail and explain exactly what his problem was or had been.
"I’ve not been feeling great," he said. "The guys at Hinsta [Performance] are overlooking everything, but I’m feeling good to drive, that’s the most important thing.
"I won’t expand on it [the condition]. It’s not an illness. It’s just something different. I’ll expand when the time’s right.”
"I felt alright last night but I didn’t know how I’d feel today. It’ll all make sense when I explain, but as I said the time’s not right now.
"The number one priority has been looking after myself, and it was always the idea that’d we’d assess after practice but obviously the team needed a back-up plan," Russell added.
"I don’t feel 100 per cent but I’m well enough to drive."
Russell concluded Friday's first practice session P20, but improved to P19 in FP2.