Kevin Pietersen has been included in the squad of 12 for England's first Ashes Test against Australia at Lord's, which starts next Thursday. Pietersen has been included ahead of Graham Thorpe, who has been struggling with a back injury. Ian Bell and Christ Tremlett have also been included in the squad.

David Graveney, England's chairman of selectors, admitted that the decision to include Pietersen caused much difficulty. "This has been the most difficult decision that I have been party to in my time as a selector," said Graveney, "with both Kevin and Graham making compelling cases for selection.

"Ultimately, we have opted for Kevin because of the form he showed against Australia in The NatWest Series and The NatWest Challenge, his excellent first-class career record and the energy and enthusiasm he brings to the England dressing room. We have no doubts that he will be able to transfer his one-day form into the Test arena and firmly believe that he has the potential to become a world class player in England's middle order and a genuine match-winner.

"The selectors do not view this decision as marking the end of Graham Thorpe's international career. He has been one of our most impressive performers with the bat since he returned to Test cricket in 2003 and, subject to form and fitness, he will continue to come under consideration for the remainder of the Ashes Test series.

"We did consider other possible permutations with the batting order. But Ian Bell has made an excellent start to his Test career, is currently averaging over 60 for Warwickshire in first- class cricket this season, and we feel that he has the temperament and the technique required to succeed against Australia. Chris Tremlett made a promising start to his international career with the one-day squad. His selection will give us another bowling option once we have had a chance to assess the wicket and the conditions at Lord's next week."

"I'm delighted," said Pietersen. "I'm the happiest boy in the UK this morning. I've got goosebumps - it's a special feeling. I ticked the right boxes, thank goodness. It's big shoes to fill, Graham Thorpe's shoes, but it's an opportunity for me now to go and cement my place in the England side and reward the people for selecting me. I put a lot of pressure on myself going into bat [at the Oval on Tuesday]. For the first time in cricket, I was really, really nervous going into the game. I put a lot of pressure on myself in terms of going out there to do well. Thank goodness I got there."

Pietersen ummed and ahhed about whether or not he would be nervous heading into the first Test next Thursday. "I've been given a positive boost by Grav and the selectors and all the public saying I should be penciled in. I said before I keep things very, very simple. It's a different game, yes, but I'm not going to blow it up and say it's a massive something. I will just give it a go. I went to South Africa and played a series there, there was loads of pressure on me but I came out all right. There was loads of pressure I put on myself on the other day but I came out of that OK. That was a difficult situation - 55 for 3 at Lord's. I'm not going to get worried about it - I'm just going to enjoy the moment keep it simple and enjoy the moment. "

However, a few moments later he admitted that he was bound to get nervous: "You're always nervous. I always knew - with missing out on a few occasions recently - that I had to make a few on Tuesday. I'm not going to say I'm not nervous because it's huge. It's the Ashes, it's Lords, and my family will be there. It's ridiculous to say I'm not going to be nervous."

Graveney said he had rung Thorpe ahead of Pietersen, to explain that there were several factors which worked against him - but mainly Pietersen's good form. "As phone calls go it was easier than some - that's to Graham's credit," said Graveney. "He was fit for selection. He's not played a lot of cricket over the last few weeks. He's not available for Test matches from the end of the season. I don't think there have been too many instances where people have indicated they are going to finish three or four months ahead. But in the end Pietersen was the decisive factor. We are looking to beat Australia - the selection of Pietersen gives us a better chance."

Graveney touched upon why Tremlett had been chosen ahead of Jon Lewis. "Chris has won the nod in this instance - but that doesn't mean that Jon won't feature in the future, and that underlines the quality in our squad." He added that he wasn't too perturbed by the fact that England have only played one-day internationals recently and no Tests since early June. "It's not a major concern. England have been playing international cricket against the best side in the world."

And he dismissed suggestions that he was worried that Australia were peaking just at the right time. "They've played some exceptional cricket in the last few matches. They played some good cricket in the last few games of the NatWest Challenge, but when the Australians arrived here we surprised them with the quality of our players. They raised the bar and we need to do that leading up to Thursday."

England squad Marcus Trescothick, Andrew Strauss, Michael Vaughan (capt), Ian Bell, Kevin Pietersen, Andrew Flintoff, Geraint Jones (wk), Ashley Giles, Simon Jones, Matthew Hoggard, Steve Harmison, Chris Tremlett.