Another big crowd packs into Lord's for the fourth day's play with South Africa 333 runs behind after having to follow on

South Africa skipper Graeme Smith swings away a leg-side delivery as he and Neil McKenzie deny England an early breakthrough

Spinner Monty Panesar reels off a series of maidens but a confident lbw appeal against Smith is rightly turned down

England's Kevin Pietersen takes time out to don a protective knee pad in case any diving in the outfield is necessary

But McKenzie opts almost exclusively for obdurate defence as he and Smith share a half-century stand and survive through to lunch

Smith reaches a 106-ball half century after lunch as South Africa raise the tempo slightly while continuing to avoid unnecessary risks

Michael Vaughan and Jimmy Anderson examine the ball as England try to find a way to separate the South African openers

McKenzie is lucky when an outside edge evades the England slips and finally reaches his fifty after almost four hours at the crease

Paul Collingwood cannot believe it as an inside edge by McKenzie just before tea runs away to the fine leg boundary

And Panesar shows England's frustration as they complete another session without reward, South Africa reaching 128-0 at tea

Smith receives the congratulations of his partner after completing a century to add to the 259 he made at Lord's five years ago

Smith has a let-off when keeper Tim Ambrose floors a chance off Kevin Pietersen's occasional off-spin

It does not prove a costly miss, however, as Smith top edges an attempted pull off Anderson and Pietersen takes the catch

McKenzie's high-concentration innings takes its toll and he requires treatment for cramp as his score reaches the 90s

The physio's work pays off as McKenzie's resilience is rewarded when he reaches his century off 307 balls shortly before the close

Hashim Amla faces a barrage of short-pitched bowling from England but keeps McKenzie company until stumps with South Africa on 242-1