The 22-year-old from Yorkshire was second behind Denmark's Lotte Friis in 8m 16.66sec while Adlington could finish only fourth

 

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Adlington was devastated following the race where she had no answer when Friis, who claimed bronze in Beijing, went out at the halfway mark.
 

Jackson overhauled Filippi in the final 20m to claim her second silver medal at the Foro Italico and third overall to add to her Olympic bronze.

 

She had earlier won a silver medal in the 400m freestyle and a bronze as a member of the 4x200m freestyle relay.

 

It was Britain's seventh medal of these Championships.

 

Jackson said: "It was such a tough race.

 

"It was so hard out there.

 

"We all just went out so fast and it was all I could do to keep going.

 

"I"ve honestly never felt so exhausted after a race."

Adlington was clearly happy for her close friend but admitted the pressure had got to her.
 

She had: "It was so tough, it was really tough.

 

"I may have over-tapered, I don't know.

 

"All week I have been finding it really hard.
 

"Coming back a year after the Olympics - there is nothing like the Olympic Games and it is a little bit of a comedown for me but I really wanted to do a PB (personal best) at this meet and that didn't happen.
 

"The 400 the first day I found really tough although I managed to pull it out in the final.

 

"I'm not having that much of a great meet,

 

"I'm just finding it really difficult.

 

"I didn't realise how much the pressure would hit once I got to the major meets."

 

Earlier, 24-year-old Liam Tancock from Loughborough had shattered the world record in the 50m backstroke semi-finals.
 

The Briton swam 24.08 to beat Randall Bal's mark of 24.33.

 

The former world record holder, Tancock, who won the bronze medal in the 50m backstroke at the 2007 World Championships, showed his power through the water as he stormed home to knock over 0.30 seconds off the previous best.

 

The star of the night was Michael Phelps (pictured), who beat Milorad Cavic to the punch again, and this time he earned a clear decision by smashing the 50-second barrier in the 100m butterfly final.

 

The American superstar clocked a world record 49.82 to beat his Beijing Olympic rival by 0.13 of a second.

Phelps had beaten Cavic by just one one-hundredth of a second in Beijing, and the Serbian turned this World Championships showdown into a grudge match.
 

Phelps's victory celebration was fierce.

 

When he saw his time, he hoisted himself on the lane rope and yelled, smacking the water in triumph.
 

Phelps said: "You can tell after my celebration that it satisfied me a little bit."

Cavic had looked to have the upper hand heading into the final.

 

He broke Phelps's world record in the semi-finals with a time of 50.01.
 

Cavic also ratcheted up the rhetoric when he offered to obtain one of his new-generation polyurethane suits for the American, who has stuck to his older model.
 

Phelps said: "It doesn't matter about the suit, it's about how you train."

Cavic also broke 50 seconds, but his 49.95 was good enough only for silver.
 

He said: "Michael Phelps is Michael Phelps, and he does what he does - and he did."

 

Britain's Gemma Spofforth and Elizabeth Simmonds narrowly missed medals in the 200m backstroke as they finished in fourth and fifth place respectively.

Spofforth, who had won the 100m earlier in the week, showed an impressive tail end as she timed her race almost perfectly.

 

She turned at the 100m mark in eighth place but pulled back to finish in fourth place in a new British record time of 2:06.66 and missed bronze by just 0.30.

Simmonds, who finished in sixth place in the Olympics, touched just outside of the personal best she set in the heats as she finished in an impressive fifth place overall.

Simmonds took the race out well and kept on the shoulder of Zimbabwe's world record holder Kirsty Coventry.

 

She turned in second place at the 50m point and Simmonds touched in 2:07.98 in her third World Championship final.

Simmonds said: “These Championships for me have been about gaining more experience and I am delighted how it has gone.

“That race was really tough.

 

"We knew it was going to be the fastest ever 200m final.

 

"A medal wasn’t realistic for me at this stage but I’m really pleased that I’ve been improving all year and my swims this week have shown that.”

The gold medal was won by Coventry in world record time of 2:04.81 with silver going to Russia's Anastasia Zueva in 2:04.94.

The women’s 4x100m medley relay team, which featured  Spofforth, Lowri Tynan, Ellen Gandy and Fran Halsall, took fourth place in the final as they broke the British record.

The quartet impressed throughout the race as they lowered the British record that was set at the Beijing Olympics.

Halsall swam the anchor leg for the Brits and fought hard but touched in fourth place in a time of 3:57.03.

The gold medal was won by the Chinese team in a new world record of 3:52.19 and Australia took silver in 3:52.58.