Swimming: Adlington is left trailing by Jackson

Rebecca Adlington marked her return to serious racing for the first time since the Beijing Olympics last night with a sensational swim here in the 400m freestyle final at the British Championships, but she still ended up losing.

In a thrilling race, the 20-year-old from Mansfield clocked 4min 0.89sec, which was inside the previous world record held by Italy's Federica Pellegrini. But in a twist that was always on the cards, although not in such a magnificent time, the race was won by Jo Jackson, in 4:0.66. That took 0.87sec off the old mark.

Adlington's two gold medals last summer came in the 400m and 800m freestyle finals. Jackson, 22, won bronze in Beijing in the 400m so last night's victory was always a possibility. She had been swimming faster this year than Adlington, and had also not had to cope with quite as many post-Games pressures.

These championships also act as the first part of the trials process for this summer's world championships in Rome. Only the winner of each final here is guaranteed a berth on the British team, so Jackson has booked her place, but Adlington has not, yet. She will now be required to swim at the Scottish national championships in Glasgow in June, which will double as the second phase of qualifying, to try to secure a place in the 400m.

For now, that will be a trifling detail. Last night Adlington was delighted just to have shown she is in decent shape, and as motivated as ever. Only last month did she finally return to 10 sessions per week in the pool plus five in the gym, and after suffering a stomach bug three weeks ago, was rated by her coach, Bill Furniss, as "operating at about 85 per cent of what she's capable of".

Adlington herself said last night: "It's never been a question of motivation. I'm motivated. It's just been a question of how to deal with [all the post-Games distractions]. I'm a girl who's only just turned 20 and I've never felt so much pressure and expectation. Nobody's trained me for that."

Jackson said: "I knew I'd been swimming well in training but I never knew I could do that. I was hoping for a British record. To get a world record is amazing."

The race itself was a cracker, neck and neck from the start, with Jackson edging ahead only in the third 100 metres before Adlington came back at her in the final straight.

Adlington will be back in action this morning in the heats of the 200m freestyle, with a semi-final this evening and probably the final tomorrow night. Tomorrow morning she will compete in heats of the 800m, in which she set a world record in Beijing, with the final on Thursday.

It is still highly likely she will be going to Rome to compete in all three individual events, as well as the 200m freestyle relay, and if nothing else, last night showed that she is capable of more.