Rebecca Adlington will arrive in Beijing on August 5 as an Olympic medal hope in two events after shattering her own Commonwealth record with a victory in the 400metres freestyle in 4min 02.80sec at the ASA National Championships in Liverpool on Sunday.

Already ranked No1 in the world this year in the 800metres freestyle, the 19-year-old from Nottingham is now also seeded third in the 400metres, a little over a stroke away from Federica Pellegrini, the world record-holder from Italy, and a hand behind Katie Hoff, of the United States. Behind Adlington was Joanne Jackson, in 4:05.49, after she set a time of 4:04.81 in the heats on Saturday evening.

“That was unbelievable,” Adlington, who is coached by Bill Furniss, said. “I don't understand how I've just done that time. I've been training hard throughout this meet, doing seven kilometres a session and then trying to race hard through it. I felt awful this morning. I've been sluggish and heavy through the water and I didn't think I could go that fast. I expected a 4:08 and would have been happy with that.”

She was happier with a time that made her fourth fastest in history and the fourth woman to race inside the 4:03.85 at which the world record had stood to Janet Evans, the legendary American, between 1988 and 2006. The first of those was Laure Manaudou, of France, who will defend her crown in Beijing after having lost the world mark to Pellegrini in March this year.

Adlington dismissed the form guide and said: “It will all come down to racing on the day. What's happened so far won't mean a thing.” Her events, the 400 and 800 freestyle, are the last two races in which British women won Olympic medals in the pool. Sarah Hardcastle and June Croft finished second and third in the 400 and Hardcastle third in the 800 at the Los Angeles Games in 1984. Croft came to watch in Liverpool and found herself having to pay for a ticket to get in. No concessions for the last woman to win an Olympic medal for Britain in the pool. No recognition either.

The national championships concluded with the disqualification of Mark Foster in the 50metres butterfly final. Having been unable to swim in the freestyle sprint on Thursday because of a prior engagement, the 37-year-old decided, against the rules, to swim freestyle in the butterfly final to show what he could do.