Morkel impressed with three wickets at Taunton

The disappointing form of spinner Paul Harris proved the only blip for South Africa as they tightened their grip on the tour opener at Taunton on day two.

Resuming on 455-3, the tourists closed on 515-3 after the mandatory 100 overs, Hashim Amla top-scoring with 172.

Pace trio Morne Morkel, Makhaya Ntini and Andre Nel then helped dismiss the Championship title-chasers for 249.

But Harris conceded 89 runs in 18.4 overs before two late wickets, with South Africa closing on 56-1 in reply.

The spinner will be needed to provide effective back-up to the quicker bowlers and all-rounder Jacques Kallis when the first Test with England starts at Lord's on July 10.

And his form will be a worry, with many suspecting England will be tempted to prepare slower wickets in an attempt to combat the Proteas's fiercesome pace attack.

Even with world number one bowler Dale Steyn rested, Morkel, Ntini and Nel made short work of the Somerset line-up, for whom only Craig Kieswetter (67no) and Wes Durston (61) provided any kind of resistance.

Morkel (3-64) was the most impressive of the South African attack and his pace is certain to provide a searching examination for Michael Vaughan's England side.

South Africa were also aided by the two needless run-outs of Zander de Bruyn and Peter Trego in mid-innings.

In reply, stand-in skipper Ashley Prince refused to enforce the follow-on and Neil McKenzie led the way for South Africa with the bat, with Jean-Paul Duminey the man out, as the tourists built a lead of 322 with nine second-inning wickets in hand.

On the injury front, Kallis and Amla - who both missed the second day's play with a bruised elbow and slight groin strain respectively - are not regarded as serious, while captain Graeme Smith should play against Middlesex at Uxbridge from Friday following a groin strain.