British Swimming Championships 2010
Dates: 29 March-3 April Venue: Ponds Forge, Sheffield
Live on BBC Radio 5 live sports extra, highlights on this website
David Davies has been well below his best at the British Championships
David Davies has withdrawn from the 1500m freestyle at the British Championships with physical exhaustion.
It means the Olympic 10k silver medallist will not be able to compete at the World Open Water Championships or the European Championships.
However, the 25-year-old has already been pre-selected for the Wales team for the Commonwealth Games in Delhi.
Davies was ninth in the 400m freestyle earlier this week in Sheffield, 14 seconds outside his personal best.
After that race the Barry swimmer told BBC Sport that it had been "a bad couple of months" and admitted he "has stuff to sort out" before he bids to defend his 1,500m Commonwealth Games freestyle crown in October.
The British Championships in Sheffield double as trials for the year's major competitions.
Withdrawing from the 1500m means Davies will now miss out on a British team place for the World Open Water Championships in Roberval, Canada, in July and the European Championships in Budapest, Hungary, the following month.
Davies' compatriot Thomas Haffield was in action in the 400m individual medley in Sheffield on Thursday evening, coming third behind European junior champion Roberto Pavoni and Joe Roebuck.
Jemma Lowe, like Davies already pre-selected for the Welsh Commonwealth team, was also third in the 100m butterfly as Fran Halsall took first with Ellen Gandy second.