England tightened their grip on the fourth morning of the third test against South Africa with debutant Tom Westley striking an unbeaten half-century as they extended their lead to 331 at the Oval.
By lunch they had reached 153-2 with Westley on 50 and Joe Root on 38 with the captain seeking to accelerate the scoring ahead of a likely afternoon declaration.
No test team has successfully chased more than 263 runs in the fourth innings to win at the Oval but there are plenty of examples of last-day defiance and Root must leave his bowlers enough time to force the victory that would put England 2-1 up in the four-test series.
Rain has already shortened the match by more than 80 overs and Root will probably be looking to set South Africa a target in the region of 450 runs.
England began the morning on 74-1, seeking to make the most of brighter conditions following Saturday's heavy rain.
Keaton Jennings was the only wicket to fall, caught by Chris Morris at gully from a ball that rose steeply from Kagiso Rabada. Jennings, who had scored just 44 runs from his first five innings of the series, made a patient 48.
At the other end, Westley, who was 28 overnight, began patiently and played within himself. Although Root dominated their partnership, scoring 35 of their first fifty from 99 balls, the Essex right-hander grew in confidence once the dangerous Morne Morkel had been seen off.
South Africa's attack lacked the potency of Trent Bridge, with Vernon Philander still affected by the stomach bug that has disrupted his test and caused him to spend the previous night on a drip.
Morris also struggled to reproduce his second-test form and England accumulated runs steadily despite a damp outfield slowing their progress.
Morkel returned for another testing spell before lunch but Westley proved up to the challenge, clipping the paceman off his legs to reach his half-century in only his second test innings.
It was fair reward for a watchful innings that should guarantee him an extended run at England's problem number three spot.
England won the first test at Lord's but South Africa tied the series 1-1 by winning at Trent Bridge. The final test is at Old Trafford.