England will go into tomorrow's First Test at Lord's knowing they must raise their game to another level after five months of playing against New Zealand - and are confident South Africa will help them do just that.

Four wins from the last five outings, two series in the bag and, barring a late injury drama, the same line-up for a record-creating sixth consecutive match: anyone just tuning into 2008 would jump to the conclusion that Michael Vaughan's side are on the crest of a wave and ready to dethrone Australia, never mind put the Proteas in their place.

But three of those four victories over New Zealand were clawed out from positions of peril and England must work on the assumption that anything more than the very occasional bad session during the summer's second npower series will cost them dear against a South Africa team unbeaten in seven straight series and capable of getting even better.

There, then, is both the danger for Vaughan's team and the spur which could help to catapult them towards second place in the Test rankings; a position at present held by these visitors.

"I think both teams are aware this is a very important series," said England opener Andrew Strauss. "That means it's going to be competitive and hard, but I think it will be played in good spirit."

Competitive? For sure. Hard? Definitely. Played in a good spirit? Perhaps we had better delay judgement on that one. But provided any rivalry between - just for the sake of argument - Kevin Pietersen and Graeme Smith is restricted to banter then even that should be perfectly possible.

What can already be taken for granted is a different brand of cricket to that which back-to-back series between England and New Zealand produced. South Africa's batsmen, from opener Smith through middle-order rock Jacques Kallis to highly-talented A B de Villiers, will present a tougher nut to crack.

And their three seriously fast bowlers will rarely try to bore out the home batsmen. Knock them out, maybe, but not line and length them to distraction.

"We need to be aware of the type of cricket we want to play and the type they're going to play against us," said Strauss, who wins his 50th cap this week. "Every side has its own character and South Africa play a certain form of cricket. Although a lot of our guys haven't played against them before there is quite a lot of experience in our dressing room now and it's just a case of getting yourselves mentally tuned.

"It's going to be positive, aggressive, attacking cricket and we've got to make sure we're ready for that.

"The New Zealand series tested us in different ways. And in some ways that attritional type of cricket is harder to play because you're fighting with yourself a lot of the time, whereas against South Africa you're pitting yourself against the opposition a little bit more. "They're trying to bowl you out, you're trying not to give an inch and it's all there in front of you."

While Strauss, Vaughan and Pietersen answered the Kiwi challenge earlier this summer, Alastair Cook, Ian Bell and Paul Collingwood failed to get going - and almost ground to a halt in the cases of Bell and Collingwood.

Both batsmen know their places are far from secure. But a change of attack could be just what they need to sharpen the mind and get the feet moving.

"More pace on the ball provides more opportunities to score," said Strauss. "If South Africa bowl well it's going to be hard work for us, if they are slightly off line there may be more opportunities to score than there were against the New Zealand's bowlers.

"But it's easy to get too focused on the pace aspect. The more crucial factor is how good they are as bowlers - and that's what we will find out in the next few days and weeks."

Strauss found South Africa's attack to his liking during the 2004-5 tour, contributing three centuries to England's 2-1 series win. But the 90-plus mph trio of Makhaya Ntini, Dale Steyn and Morne Morkel now offer a more potent threat.

"It can be unhelpful to look back too much because I've changed as a batsman and they've changed as bowlers," said Strauss who, like Pietersen, might have been playing for the opposition if he had stuck with the country of his birth.

Not that many people remind him of that fact with Pietersen's background to concentrate on. "I think I slipped under the radar," says the left-hander when asked whether he has copped much flak from South African opponents or fans.

Apart from scoring big runs, Strauss's other concern this week will be for his heavily pregnant wife, Ruth. But unless Mrs Strauss's timing is spot on - and she produces the couple's second child when her husband is not on the field - there will be no dash from Lord's to hospital. "My wife understands," he said.

It would be understandable, too, if England's attack tried to step up a gear this week in order to get a little nearer South Africa's pace. Understandable but a big mistake, according to the wise beyond his years Stuart Broad.

"The key for us is not to try to match their pace and bounce," said the 22-year-old. "We need to stick to what we've done well in the past four or five Tests. We've got two world- class swing bowlers with the new ball in Jimmy Anderson and Ryan Sidebottom and we just need to stick to the game plans that have worked."