Jessica Ennis has insisted that she will still have to be at her very best tomorrow to ensure that she claims gold in the heptathlon.

The British athlete currently leads the pack after four events, setting two personal bests in the process.

Despite dominating the opening day, the 26-year-old is adamant that there is "still a lot of hard work" ahead of her.

"I'm going to have to have a really strong day tomorrow," she told BBC Sport. "Everything is going to have to be where it needs to be. There's still a lot of hard work to do."

The three remaining events are the long jump, javelin and 800m.