Laura Stephens joined forces with Olympic gold medallist Ruta Meilutyte to win gold at the British Gas ASA National Championships, in Sheffield.
The Colchester Swimming Club member, who now competes for Plymouth Leander, followed the Lithuanian on the fly leg to help the team win gold in the 4x100 metres medley relay.
Meilutyte, 17, who claimed gold at London 2012, is the current 50m and 100m breaststroke world-record holder.
Stephens, the former Colchester High School for Girls pupil, also helped her club won gold with her Plymouth team-mates in the 4x100m freestyle relay at Ponds Forge.
For more on this story, see Wednesday's Daily Gazette.