SHANGHAI, July 30: Michael Phelps, already the most successful Olympian of all time, picked up his third successive world 100 metres butterfly title on Saturday.

The American clocked 50.71 seconds to clinch his third gold of the championships in Shanghai and then said he could only get better ahead of next year's London Games.

“The 50.71 is okay for now but there's a lot of improvement to make before London,” said Phelps.

Teenager Melissa Franklin, on her debut at the championships, almost stole the spotlight from Phelps when she won two golds in different disciplines.

The 16-year-old claimed her first title in the 200 backstroke and then swam the freestyle leg as United States lifted the 4x100 medley relay gold.

It was the first time the US had won the medley relay since 1998. China finished second and Olympic champions Australia took bronze in the final race of the day.

Olympic champion Rebecca Adlington also showed she was heading in the right direction ahead of the London Games with a thrilling finish in the 800 freestyle final.

The Briton, who took silver behind Federica Pellegrini in the 400 freestyle last weekend, battled with 2009 Rome world champion Lotte Friis stroke for stroke before pipping the Dane on Saturday.

Friis led on virtually each lap. Adlington made her move at the halfway mark before her rival surged again to move in front for the next 300 metres.

The Briton, trailing by half a body length with 50 metres to swim and roared on by the home crowd, then turned on the after-burners to win her first world crown.

Brazil's Olympic champion Cesar Cielo put the spectre of a possible doping ban well and truly behind him when he retained his 50 freestyle world title.

The 24-year-old, who also won the 50 butterfly on Monday, was cleared to compete just three days before the championships when the Court of Arbitration for Sport ruled he had taken ‘sufficient precautions’ in handling his supplements.

Cielo had said the supplements were contaminated and were the cause of a positive test for the banned diuretic furosemide.

Dutchwoman Inge Dekker was first in the women's 50 butterfly, edging out world record holder Therese Alshammar of Sweden.

Results of finals: Men’s: 100 metres butterfly: 1. Michael Phelps (US) 50.71 seconds; 2. Konrad Czerniak (Poland) 51.15; 3. Tyler McGill (US) 51.26; 4. Jason Dunford (Kenya) 51.59; 5. Takuro Fujii (Japan) 51.75; 6. Evgeny Korotyshkin (Russia) 51.86; 7. Joeri Verlinden (Netherlands) 52.21; 8. Geoff Huegill (Australia) 52.36.

50 metres freestyle: 1. Cesar Cielo (Brazil) 21.52 seconds; 2. Luca Dotto (Italy) 21.90; 3. Alain Bernard (France) 21.92; 4.

Nathan Adrian (US) 21.93; 5. Bruno Fratus (Brazil) 21.96; 6. Krisztian Takacs (Hungary) 21.99; 7. George Bovell (Trinidad & Tobago) 22.04; 8. Gideon Louw (South Africa) 22.11.

Women’s: 200 metres backstroke: 1. Melissa Franklin (US) 2:05.10; 2. Belinda Hocking (Australia) 2:06.06; 3. Sharon van Rouwendaal (Netherlands) 2:07.78; 4. Daryna Zevina (Ukraine) 2:07.82; 5. Elizabeth Beisel (US) 2:08.16; 6. Meagen Nay (Australia) 2:08.69; 7. Elizabeth Simmonds (Britain) 2:08.76; 8. Alexianne Castel (France) 2:09.07.

50 metres butterfly: 1. Inge Dekker (Netherlands) 25.71 seconds; 2. Therese Alshammar (Sweden) 25.76; 3. Melanie Henique (France) 25.86; 4. Sarah Sjoestroem (Sweden) 25.87; 4. Lu Ying (China) 25.87; 6. Yuka Kato (Japan) 26.02; 7. Dana Vollmer (US) 26.06; 8. Marieke Guehrer (Australia) 26.21.

800 metres freestyle: 1. Rebecca Adlington (Britain) 8:17.51; 2. Lotte Friis (Denmark) 8:18.20; 3. Kate Ziegler (US) 8:23.36; 4. Chloe Sutton (US) 8:24.05; 5. Boglarka Kapas (Hungary) 8:24.79; 6. Katie Goldman (Australia) 8:29.20; 7. Wendy Trott (South Africa) 8:30.45; 8. Lauren Boyle (New Zealand) 8:32.72.

4x100 medley relay: 1. US (N. Coughlin/R. Soni/D. Vollmer/M. Franklin) 3:52.36; 2. China (Zhao/Ji/Lu/Tang) 3:55.61; 3.

Australia (B. Hocking/L. Jones/A. Coutts/M. Dingjan) 3:57.13; 4. Russia (A. Zueva/Y. Efimova/I. Bespalova/V. Popova) 3:57.38; 5. Japan (A. Terakawa/S. Suzuki/Y. Kato/Y. Matsumoto) 3:57.84; 6. Britain (G. Davies/S. Tadd/E. Gandy/F. Halsall) 4:01.—Reuters