Ollie Pope scored his first century for England to steer them to a lead of 302 over South Africa A on day two of the warm-up match in Benoni.
England declared on 456-7 in a match downgraded from first-class status because of illness affecting the tourists’ squad.
Jofra Archer, Stuart Broad and Jack Leach returned to training on Saturday after suffering from flu-like symptoms.
The hosts closed the second day on 154-2.
Pope’s 132, which followed Joe Denly’s century on day one, will not go into the record books, because of the downgrading of the match. That allowed England to use more than 11 players and the game was reduced to three days from four because of the sickness in camp.
“It felt good. I have got close a few times, but it is a good feeling to get it out the way,” said Pope.
“If it was the first Test it would be even nicer, but it is all about the getting ready for that game.”
James Anderson (1-20) and Ben Stokes (1-24) took the two South African wickets.
Somerset bowlers Dominic Bess and Craig Overton were called up on Friday to provide cover for Archer, Broad and Leach.
The trio had a net session for the first time on Saturday but are unlikely to feature on the final day of the match against South Africa A.
This is England’s final warm-up game before the four-Test series against South Africa begins on 26 December.