Former England batsman Geoffrey Boycott has admitted that he "didn't understand" why Graeme Swann was left out of the team to play South Africa in the second Test at Headingley.

England decided to select four pace bowlers ahead of Swann in Yorkshire, a decision that has surprised Boycott. The commentator has also questioned Andrew Strauss's decision to bowl first in the match.

Boycott told BBC Sport: "I'd have batted first and I also didn't understand why they left Swann out, he's the best spinner in the world.

"I'm trying to work out why they fielded first, maybe they were worried about (Dale) Steyn, maybe they felt they needed to take some early wickets to put South Africa under pressure."

Alviro Petersen scored a century on day one as the Proteas reached stumps at 262-5.