Michael Vaughan reckons England's Test team are progressing nicely after their series victory over New Zealand.

Ryan Sidebottom's destructive fourth-morning burst meant England wrapped up an innings-and-nine-run victory over the New Zealanders at Trent Bridge in rapid time to seal a 2-0 win.

Vaughan's men have now triumphed in four of five Tests against the inexperienced Black Caps.

That sequence has catapulted them back up to third in the official International Cricket Council Test rankings but the sterner challenge will come over four matches against South Africa.

"I never envisaged winning by an innings but full credit to the way we've played our cricket, the catching was very good in this game and the win here suggests we have got better as the series has gone on," said Vaughan. "We also know there are areas to improve and the South Africa series, as I have said all summer, will be the ultimate test of where we are at as a Test team."

England hope to throw talismanic all-rounder Andrew Flintoff into the mix for that series, although he will have only one LV County Championship match to prove himself ready for the Lord's Test on July 10.

Vaughan has been clear and consistent in wanting 2005 Ashes-winning hero Flintoff back at the earliest opportunity.

And defeated New Zealand captain Daniel Vettori spelt out just why from a neutral perspective when comparing the strength of this current England unit to the vintage of four years ago when he last toured here.

"I suppose there is always that dangling of Flintoff in the corner and if you throw him in the mix then you have got a very complete team," Vettori said. "Once he comes back then it is going to be a very tough side to beat for anyone. "The England-South Africa series will be a very good one to watch."

England have had to get used to playing without Flintoff - he has not played Test cricket since the loss in Sydney in January 2007 - but will have a tough selection decision to make if everyone remains fit in the interim.

Since coming back from a fourth ankle operation, the 30-year-old Lancastrian has been in poor form with the bat, strengthening a case for him to return in a four-man bowling attack. "I hope he will get his side right in the next few weeks, get enough cricket and be confident in himself and in his form that he can take on the South Africans," Vaughan said. "You would love five (bowlers). "But I am also happy with four, it can work, and the balance of the team has to be very important when you play a good team like South Africa.

"It will probably be Freddie who will have to make the call: if he is confident enough in his own form and his body whether he plays against South Africa. "Everyone knows that, if he is fit, I would love to have him in the team."

England have flaws to iron out before Graeme Smith's Proteas arrive here in a fortnight.

As has become a feature of their cricket, England had to dig themselves out of a hole to secure victory - this time from a position of 86 for five after being asked to bat first.

"It is a position we would like not to have been in but the partnership between Kevin Pietersen and Tim Ambrose set us up for a good score," said Vaughan. "I'm encouraged by the way we're getting out of them but I would like not to get into those positions. "A sign of a good team is getting out of them but a sign of a really good team is not getting into them in the first place. "Those are the areas we can improve but we are a young side developing.

"We have won four out of five now and in every one of those wins we have got better and better. "You do tend to get better the more you play together and what pleases me most is that it has not been the same people doing it in every game. "In every game every bowler has stuck their hands up at certain times and every batsman has got us through some tricky positions whether it be in New Zealand or over here."

New Zealand, meanwhile, were left to rue their trend of relinquishing advantages.

"It sums up the state of affairs that we are in," said Vettori, whose team were blown away by man-of-the-match James Anderson in swinging conditions on the second day. "We are able to compete for a period of time but unable to compete for a whole five days. "If you look back at the six Test matches, the only time we did that was in Hamilton and we won. "Unfortunately every other time we haven't been able to keep up with the pace of England. I suppose it is a lack of ability on our part and a lack of fortitude as well."