Olivier Panis, who broke both legs in a high-speed crash at the Canadian Grand Prix in June, tested his Prost-Mugen-Honda at the Magny-Cours circuit for the first time since his crash.
The Frenchman lapped the track in 1min 14.5sec - equalling the time Michael Schumacher recorded to claim pole position at this year's French Grand Prix.
Reports last week had suggested Hill was in negotiations with Prost over a pounds 5m deal to race for the four-time world champion's team next year - and, as the current No 1 driver, Panis' position appeared to be under threat. But his return from injury may have convinced Prost to stay loyal to his current driver, who was lying third in the world championship table before his accident.
"Olivier's performance has impressed me enormously," Prost said. "There is a big step between what we are doing this week and a race weekend proper, but I am convinced the worst is now behind us."
Panis said: "My drive in a Formula Three car last week reassured me I was still competitive and that my legs had recovered and this first run in a Formula One car has confirmed that. But the work has only just begun. I have always said I would not race in a grand prix until I had recovered 100 per cent."
Panis may now make his return as early as the Luxembourg Grand Prix, which takes place at Germany's Nurburgring on 28 September.Reuse content