Katie Ledecky is the teen bolter who came from an 8:37 one season to take Olympic gold in 8:14  the next over 800m at London 2012. Now just 16, she's developing fast: having won the 400m at the Mesa Grand Prix in the US on Thursday, she went shorter still and upset the 200m free crew with a 1:56.93 win 0.03sec ahead of Missy Franklin, no others inside 2min.

Mid-season: amazing progress. Ledecky's best in a solo 200m was a 1:58.66, from Olympic trials last year. With Franklin to fire faster as the season unfolds and the likes of Camille Muffat and Allison Schmitt in the wings and waiting to rejoin battle, Ledecky (on 1:59.95 at the 200m in the 800 as pace-settter at London 2012) may not feature in the big showdowns over 200m but her new speed indicates a storm waiting to happen over 400m - and standard-setting moments over 800m and 1500m.

How Ledecky chased down Franklin:

• 28.19  57.45 (29.26) 1:27.57 (30.12) 1:56.93 (29.36) Ledecky
• 27.46  56.79 (29.33) 1:26.77 (29.98) 1:56.96 (30.19) Franklin

Franklin, still 17 herself, rejected US 'pro' status - but in approach she is a model of it: the double Olympic backstroke champion bounced back for a 2:09.35 win in the 200m backstroke ahead of Elizabeth Pelton, on 2:12.37. 

In other action, Olympic 100m champion Nathan Adrian scorched the 50m free in 21.72 ahead of Anthony Ervin, 22.31, while Natalie Coughlin took the 50m free for women in 24.90, that being the first personal best the 100m back Olympic champion of 2004 and 2008 has set in five years.

Olympic 200m backstroke champion Tyler Clary took a brace of victories, on 4:24.90 in the 400IM and 1:58.13 in the 200m back ahead of Ryan Murphy, 1:59.28 and Olympic 100m back champion Matt Grevers, 1:59.92.

Hungary’s world cup queen Katinka Hosszu claimed the 400IM in 4:40.01 ahead of Sweden’s Stina Gardell, 4:42.26, and Caitlin Leverenz, 4:42.64, while Ricky Berens took the 200m free in 1:48.93 ahead of South Africa’s Darian Townsend, 1:49.61 and Denmark’s Anders Nielsen, 1:49.67.