The normally reliable Bell was dismissed after a meagre six when his poor effort was comfortably caught by Ryan Harris before two quick leg before wicket
decisions saw Matt Prior (17) and Jonny Bairstow (14) depart as Peter Siddle claimed his first wicket of the day while Lyon claimed his fourth.
However, Perera had the left-hander trapped leg before wicket
with a sharp delivery that caught the batsman on his crease.
That surge was spearheaded by Napier, who struck three sixes in an over against spinner Tom Smith before falling leg before wicket
to McLaren for 23 in the next over.
Anderson came back to remove Ambrose, leg before wicket
for 43, and Barker was last out for 25, hoisting a catch to extra cover off Kerrigan.
40 Ayr In cricket LBW stands for leg before wicket
South Africa's first innings came to an end just after lunch when Saeed Ajmal's off-spin caught Morkel leg before wicket
England's hopes of saving the match suffered a major blow shortly before the close when Kevin Pietersen was leg before wicket
to Dale Steyn, two balls into the fast bowler's last spell of the day.
James Hopes was dropped on 10 by Umar Gul at third man off the bowling of Ishant Sharma but the error did not prove costly as Gul made amends shortly afterwards to trap the opener leg before wicket
Yasir Hameed was the man out, trapped leg before wicket
playing half-forward to Anil Kumble for 19.
The leg before wicket
decision was so obvious that Johnson did not even contemplate asking for a review, departing for the dressing room immediately.
Sri Lanka's Dilruwan Perera bagged A B de Villiers wicket as the batsman got leg before wicket
for his individual score of 37 runs.
Just two were added to the overnight score when Graeme Swann trapped potential dangerman Haddin (13) leg before wicket