Rebecca Adlington, Great Britain\'s last gold medal hope in the pool, is set for another battle royal with Danish rival Lotte Friis in the defence of her 800m freestyle Olympic crown. Adlington, the darling of British swimming after her 400-800m freestyle double triumph in Beijing four years ago, shaded Friis by just 0.11sec as the fastest qualifier in Thursday\'s heats at London\'s Aquatics Centre. The 23-year-old relinquished her 400m Olympic title when third in last Sunday\'s final behind France\'s Camille Muffat, but the longer distance suits her chances after she won the 800m title in Beijing in world record time. Adlington goes into Friday\'s final as the top-ranked swimmer in the event and faces another duel with Friis, whom she edged out for the world title by 0.69secs in Shanghai last year. The British heroine clocked 8:21.78 in Thursday\'s heats and will now be under pressure from an expectant nation to bring home the gold in the final. \"I am pleased with that. I didn\'t know what time I was going during that one at all,\" Adlington said. \"I just put my head down and went for it, especially after the 400m heat, only scraping in (to the final). \"I was like \'I am not risking that even if I give it a little bit more than I should do, I\'d rather get in safely\' so I just went for it and I am pleased with that time. \"Obviously, it\'s going to be a battle tomorrow (Friday) but I\'ve just got to see what I can get.\" Friis, who lost her world title to Adlington last year, is anticipating deafening crowd support for her rival\'s bid to capture that elusive home swimming gold. \"My goal is just a medal, then we will have to see whether it is first, second or third,\" Friis said. \"Adlington is the home crowd favourite, the world and Olympic champion, so she is the one to beat for all of us. \"She had a shaky start in Shanghai, so I am not underestimating her at any point.\" American Katie Ledecky looms as another medal chance with her third-fastest time of 8:23.84. \"It was my first Olympic race, so I went in with a lot of adrenalin and a few nerves, but it carried me through the first 400m and I finished with a solid time,\" Ledecky said.