Alastair Cook made the most of England's short ration of cricket, before the inevitable rain intervened to limit the tourists to less than half of the first day at Buffalo Park.
Cook's share of 142 for three was an unbeaten 66, while Kevin Pietersen - still searching for a first big score before next week's first Test - had to settle for more modest gains.
Cook, who also made a half-century for the England Performance Programme team in Pretoria last week, shared 50 stands first with Pietersen and then Paul Collingwood - after captain Andrew Strauss and Jonathan Trott had both gone cheaply.
He could reflect with satisfaction on his 96-ball 50, as he continues to recover from a back injury, but insisted too that Pietersen's 25 was a step in the right direction.
The opener is "managing" his back trouble and is confident he will be able to continue to do so through the remainder of the tour.
"I still do feel it. It's quite major when you have two prolapsed discs - but I can move fine out there now," he said.
"The first week with it is always weird, with back spasms, and you think you'll never be able to move properly again."
Cook was taken off the one-day international leg of England's tour because of his injury, first undergoing treatment with the Performance Programme before playing for them.
"It's been really good having that one-to-one treatment for my back, which is what I've needed," he added.
"When you're part of the squad, it is very hard to leave the lads. But sometimes, injury forces you to do that.
"It's worked well for me. The aim was to get back for the Test match - which we seem to be doing."
The next stage of Cook's rehabilitation could not have gone much better today on a stodgy wicket which showed the effects of the past week under cover.
As more rain swamped the ground again this afternoon, prospects for play on the final day of two tomorrow were not obvious.
But England then have a second two-day match scheduled against the same opponents at the same venue.
"What we've got to get out of the next three days are the personal things of bowlers getting two or three spells and batsmen some time in the middle - so I'm very happy," Cook said.
England recovered this morning from the early losses of Strauss and Trott, after the touring captain chose to bat first in initially glorious conditions.
But he could then manage only a single, and new batting find Trott was gone too by the ninth over - both caught-behind victims of former Northamptonshire seamer Charl Pietersen.
Strauss pushed out at one that bounced a little more than expected.
Trott was immediately under way with England's opening boundary from the first ball he faced, guided between slips and gully off Pietersen.
But when he tried to drive the same bowler soon afterwards, he too edged behind.
That gave England's Pietersen another chance, as he continues his return from four months out after Achilles surgery.
The South Africa-born batsman might have had an lbw scare first ball, had his namesake not over-stepped, and also had a close call when he involuntarily inside-edged a single past leg-stump off first change David Wiese on eight.
Pietersen was clearly prepared to be patient as he tried to get a foothold, and had to wait for his first boundary - a full toss smashed past extra-cover off Wiese - to bring up the 50 partnership.
Cook, by contrast, had already fed off some unwise short-pitched deliveries from Siya Ntshono on a sluggish surface.
He soon began to drive as well as pull with authority, and Pietersen joined in - only to depart just before lunch.
It was unjust reward for his hard work when an unremarkable ball from Wiese stopped on him as he shaped to make runs off the back foot and instead fell to a one-handed return catch high to the seamer's right.
Cook - who completed his 50 in early afternoon before the weather broke, with his seventh four forced past cover off slow left-armer Piet van Niekerk - believes Pietersen will have derived significant benefit from his latest contribution.
"It's very much a patience game. You can't really hit through the line. When they do drop short, that's your chance," he said.
Pietersen's dismissal, he agreed, was unfortunate.
"It just stopped on him a little bit," Cook added.
"But he's looking at it as another hour spent in the middle.
"He is our best batter and will be ready for the first Test next week.
"It's a gradual process, having been out for so long.
"It doesn't matter how many nets you have. It's all about middle time.
"But he's building back up and has had a bit more of a smile on his face today after even spending an hour out there."