England were 82 for four at lunch, with Philander having taken three wickets for 26 runs in eight overs. Joe Root, England's new Test captain, was 33 not out and Ben Stokes, his vice-captain, unbeaten on four.
Root perhaps encouraged by the blue skies overhead and Lord's reputation as a good batting pitch, opted to bat first after winning the toss. But a green-tinged pitch also gave the bowlers hope of early movement.
Alastair Cook in his first Test since resigning as England captain in February, had made just three when he flat-footedly chased a Philander delivery outside off stump and edged to wicket-keeper Quinton de Kock.
Cook's fellow left-handed opener was lbw to Philander for eight after not getting that far forward.
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S Ravi took his time before raising the finger, with England eventually opting against a review.
Replays, which showed the ball had just pitched outside leg stump, suggested a challenge might have seen the Indian umpire's decision overturned.
The 32-year-old Philander, fit following an ankle injury sustained while playing for English county side Sussex, had once again shown that an ability to move the ball both ways at a lively pace more than compensated for a lack of express pace. He'd now taken two wickets for three runs in eight balls to leave England 17 for two.
Root, meanwhile, was fortunate, when on five a top-edged hook off Kagiso Rabada just cleared substitute fielder Aiden Markram at long leg.
Jennings's dismissal may have had some influence on the exit of the third left-handed member of England's top three, Gary Ballance.
Recalled for a third crack at Test cricket after churning out the runs for Yorkshire this season, Ballance was lbw to fast bowler Morne Morkel, altering his delivery angle to around the wicket, for 20.
Jonny Bairstow had performed many a rescue mission for England with the bat. But on Thursday the wicket-keeper fell for just 10 when he made the mistake of going back to a full- length Philander delivery that hit the seam and smacked into his pad.