By Jonathan Agnew BBC cricket correspondent at Headingley

England recovered well after Vaughan fell early on

This match could not be more perfectly poised.

At 197-3, England are 145 runs behind the South African total of 342.

But the pitch is still playing enough tricks to make batting awkward, particularly for those who have just arrived at the crease.

England appear to have shot themselves in the foot by accepting an offer for bad light on 164-1, and having just scored 23 runs from 17 balls.

As Graeme Smith agreed, South Africa were bowling "rubbish", but Trescothick and Butcher thought long and hard, and there was widespread amazement when they trooped off.

The batsmen were completely in control and relishing the wayward bowling that was on offer.

Quotes: Butcher defends light decision

But the half hour stoppage affected their momentum and, shortly after they returned to the middle, Trescothick was brilliantly caught and bowled by Kallis for 59.

Then Butcher was caught behind for 77 off the same bowler 6 overs later.

With Hussain and Smith then playing themselves in, the game looked very different.

Butcher should have played on when batting so well

The ball snaked past the outside edge several times, so there was never any question of the batsmen deciding to stay in the firing line when the light was offered to them a second time.

Bad light has long provided much debate, and it is rarely straightforward.

This has been complicated even further by the new regulation that allows lost time to be made up the following day.

This gives the batting team no incentive to stay in the middle in dodgy light because they know that they can bat in better conditions the next day.

However, as Ray Illingworth always said: "Do what the opposition don't want you to do."

Delighted

On this occasion, the South Africans were delighted to get off the field: enough said.

South Africa added a further 82 runs in the morning with Kirsten finally dismissed for 130, Ntini making 32 not out.

This seemed to be at least 100 runs more than South Africa should have got when they were 142 for 7.

And had they bowled more accurately, they might have had England in real trouble.