Lewis is determined to defend her crown after a string of injuries

The 31-year-old, who has battled back from an ankle injury, says she is now both physically and mentally tougher than when she clinched gold in Sydney.

"I lost a chunk of the season through injury but I am happy with where I am," said Lewis. "I am in better physical condition than I was four years ago.

"There are five or six girls fighting for a medal and I am one of those."

Just six weeks ago, Lewis was considered a doubt for the Athens Games after she aggravated a foot injury at the British trials.

But Lewis showed her characteristic grit to get back to fitness and is aiming to improve on her last competitive heptathlon at the 2003 World Championships, where she finished fifth.

Mentally I don't know if I can cope with the pressures of a global championships British heptathlete Kelly Sotherton

"I have had a rollercoaster year and I am glad to be here," added the Birchfield Harrier.

"I love the unpredictability and the challenge of pushing myself to be better in each event."

Lewis can expect to face a stern test in Athens in the shape of Sweden's world champion Carolina Kluft.

But the emergence of the Isle of Wight's Kelly Sotherton means she also finds competition within the British squad.

Academy: Watch Denise's shot put masterclass

The 27-year-old is contesting her first Olympics but ranked third into the world she is a serious medal contender.

"Physically I think I could medal because I am flying in training and couldn't be in better shape going into a major Games," said Sotherton.

"But mentally I don't know if I can cope with the pressures of a global championships.

"I might be in better shape than Denise physically but she's got it up top and that's what got her a gold medal in Sydney."

The British pair will get their heptathlon challenge underway in the 100m hurdles, the high jump, the shot and the 200m on Friday.