England 353 and 74 for 1 (Jennings 34*, Westley 28*) lead South Africa 175 (Bavuma 52, Roland-Jones 5-57) by 252 runs
As rain put a dampener on The Oval's 100th Test celebrations, one England batsman was concerned not with marking the past but protecting his future.
Keaton Jennings' England place was under threat after making only 44 runs in his first five innings against South Africa, his hundred on Test debut against India in Mumbai in December now a distant memory.
Jennings was 34 not out - his best score of a draining summer - when rain arrived shortly before 3pm and prevented further play. England, at 74 for 1, were building an impregnable position, leading by 252 with nine wickets remaining, but will fear more disruption from the weather over the last two days. As for Jennings, he was just relieved that one of those nine wickets remains his.
Vernon Philander had been conditionally discharged from hospital, coming out to bat for South Africa at No. 11 as they were dismissed before lunch for 175 and then summoning what strength he had left for a few below-par overs.
His viral infection had not yet departed and he was still vomiting and suffering from abdominal pain. But NHS nurses presumably got him back on his feet by whispering the words "Keaton Jennings" kindly into his ear because it has proved to be a pick-me-up all series.
Jennings was chary against Philander from the outset and might have fallen twice in successive balls in his second over. He inside-edged past leg stump for his first boundary, looking round uncertainly as if he had stumbled over a paving slab. The next ball, on 6, he was dropped by Dean Elgar, head high at third slip. South Africa's cordon was bunched and close and, on this occasion at least, suffered for it.
Jennings routinely stands as straight as a sentry at the crease. Put him in a bearskin hat and he could easily double as a guardsman at Buckingham Palace where he would have the discipline to stand still for hours while tourists snapped away intrusively. But it was movement, not stillness, he hankered after and he danced around on the spot in an attempt to rid himself of the stilted footwork that has bedevilled him all series.
Alastair Cook departed for 7, undone by a top-notch delivery from Morne Morkel which he straightened from around the wicket to crash into the top of off. Too good for Cook, one imagines it would have defeated Jennings, too, but he watched from the non-striker's end, a batsman spared.
Kagiso Rabada's first over afforded a release. He had the poise to crash two short and wide deliveries through the off side. In the next over, he tucked Morkel off his pads for another boundary: 19 and vulnerable had become 32, a score to build on, in a matter of five minutes.
Not that he suggested permanence. He needed a review to survive an lbw decision in Rabada's favour on 33, replays suggesting the ball had both pitched outside leg and would have passed over the stumps.
While Jennings struggled, Tom Westley again played with elan, six boundaries in his 28. The best of them as far as Jennings was concerned was the one that persuaded Philander to leave the field for another toilet break. Before too long, everybody followed him into the dressing room, never to re-emerge.
The morning belonged to Toby Roland-Jones, who completed a five-wicket haul on Test debut as South Africa were dismissed for 175 - a deficit of 178 . Eight down for spit overnight, with Philander carded at No. 11, South Africa might have folded in no time. Instead they added another 52 in 15.4 overs.
Roland-Jones led England from the field, raising his cap slightly bashfully, after returning 5 for 57- the first English quick to take a five-for on debut since Graham Onions in 2009. His last wicket was a good one: Temba Bavuma pushing forward to a ball that left him to fall to a keeper's catch after making 52 from 120 balls.
Bavuma had been a serene figure even on the previous evening, as South Africa collapsed to 61 for 7 with the floodlights cutting through a grouchy south London evening, and he looked at ease again in what were initially more inviting batting conditions.
The stumps were blue to mark Cricket United day, as were much of the crowd, an annual fund-raiser at The Oval for three charities. It is a pragmatic choice. If you are going to ask a fair proportion of blokes to dress up in a colour for charity, it's best to choose blue. It's all some have in their wardrobe.
After his dream sequence on the second day, Roland-Jones found life had returned to normal as he began at the Vauxhall End. The comparison between him and the quick he replaced - Mark Wood - is instructional.
Roland-Jones is a classic English seamer, hitting the seam at an average of 83mph. Wood is the sort of explosive quick needed on more benign surfaces. But Wood has only averaged 86mph in his two Tests against South Africa. Averages tell only half the story, of course, as the potential for an occasionally quick ball is also important, but explosive bowlers need to explode.
Bavuma had attractive moments, particularly when driving through the off side, striking Stuart Broad to the extra cover boards to take South Africa past the follow-on and then stretching his diminutive frame to the utmost to plant Anderson in the same direction, although he was dropped off Broad on 40, Ben Stokes failing to cling to a rapid chance as he dived to his left in the gully. His half-century was also raised streakily when he edged Roland-Jones wide of the slips.
Morkel also put up stubborn resistance, reaching 17 before he edged a back-of-a-length delivery from Anderson to Cook at first slip.
Roland-Jones might have picked up Philander on 5, but his edge flew wide of third slip. A one-legged flat-bat then lobbed over mid-off. But Philander survived, albeit not particularly healthily. He, at least, would have welcomed the rest.