Kevin Pietersen defended the extravagant sweep shot that cost him his wicket and let Australia off the hook towards the end of a compelling opening to the Ashes series in Cardiff yesterday.

Pietersen and Andrew Flintoff, the leading lights of England’s triumph in 2005, made presents of their wickets when set fair. While a total of 336 for seven represented a better start to the first npower Test than in the previous two contests between the countries, England could have been in a dominant position but for those lapses.

Pietersen was England’s top scorer with 69, but he left himself open to criticism for attempting to paddle a ball from Nathan Hauritz, the off spinner, from well outside off stump only to top-edge an easy catch to short leg.

Television pictures captured Pietersen back in the dressing room banging his head with his hand in frustration when he saw a replay of the stroke. Later, however, he denied that he had given away his wicket.

“You guys look deeper than I do,” Pietersen said. “When you are out, there is nothing you can do about it. I was unfortunate to hit the ball on to my helmet, otherwise it would have been a single to fine leg.

“Hauritz probably outfoxed me. I thought he bowled very good lines and varied his pace. He does not have the mystery spin of a [Muttiah] Muralitharan or [Ajantha] Mendis but he is a clever bowler, he knows what he is doing. He is not a fool.”

With the pitch starting to turn and Australia due to bat last against Monty Panesar and Graeme Swann, a first-innings total of about 400 would give Andrew Strauss’s team a chance to make a winning start. That was jeopardised, though, as six of the top seven batsmen fell for between 30 and 69.

Pietersen, though, found an unlikely ally in Tim Nielsen, the Australia head coach. “That is the way he plays,” Nielsen said. “He swept probably 15 times before that pretty well. If a guy nicks a cover drive, you don’t tell him to stop cover driving.”

England won an important toss, given the composition of their side, and based their innings on two big partnerships. Pietersen and Paul Collingwood added 138 for the fourth wicket before Flintoff and Matt Prior put on 86 in 95 balls either side of tea.

In both cases, however, the two batsmen fell in quick succession and Flintoff, having shown signs of being close to his best, was annoyed with himself for chopping a wide ball from the persevering Peter Siddle on to his stumps.

Nielsen said: “I thought that if they [Flintoff and Prior] were both not out overnight and still going in the morning with the ball hard and the pitch as good as it is going to be, we would be under a lot of pressure.”

The first session this morning promises to be critical. “It will be important for us to get close to England in our first innings,” Nielsen said. “We have to bat our backsides off. There is no doubt the pitch will deteriorate and batting will become pretty difficult over the last day and a half.”

Pietersen noted that Hauritz has turned the ball from the straight and Mitchell Johnson, Ben Hilfenhaus and Siddle, the Australia seam attack, have created rough on the surface.

“I could be greedy and say we would like to be four or five wickets down and maybe Collingwood and myself missed opportunities to make really big scores,” Pietersen said. “But in the previous Ashes series I have played in, Australia dominated the first day.

“I think this was a pretty good first day for England and the help for the spinners makes it pretty interesting.”

The day was a success for Glamorgan, who want to bring Ashes cricket to the SWALEC Stadium on a regular basis. Australia play a one-day international at the ground next summer and Sri Lanka a Test match in 2011.