EVENT 509 Female 400m Freestyle - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 1 | Charlotte Ryan | 24 | S6 | Runnymede | 9:00.81 |
| 2 | 3 | Emily-Grace Bentley | 14 | | Basildon Ph | 4:44.74 |
| 3 | 5 | Niamh O'Meara | 18 | | Watford SC | 4:43.51 |
| 4 | 7 | Eleanor McLeod | 16 | | Putteridge | 4:41.93 |
| 5 | 6 | Amy Harper | 17 | | Watford SC | 4:42.20 |
| 6 | 4 | Miriam Moukdad | 18 | | Bishop Stort | 4:43.83 |
| 7 | 2 | Abigail Wickens | 17 | S8 | Flitwick | 5:30.70 |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 9 | Amelie Crabb | 17 | | teamipswich | 4:39.64 |
| 2 | 11 | Florence Crowley | 18 | | Co St Albans | 4:37.55 |
| 3 | 13 | Almudena Visser Velez | 22 | | Co Cambridge | 4:36.59 |
| 4 | 15 | Millie Richardson | 18 | | Hatfield | 4:35.87 |
| 5 | 14 | Amelia Porzio | 16 | | Putteridge | 4:36.46 |
| 6 | 12 | Francesca Howell | 16 | | New Hall | 4:37.03 |
| 7 | 10 | Anabelle Kett | 15 | | Co Peterboro | 4:38.30 |
| 8 | 8 | Amelia Saunders | 16 | | Norwich Swan | 4:40.20 |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 17 | Jessica Medlicott | 17 | | Dunstable | 4:34.90 |
| 2 | 19 | Gabriella Troman | 15 | | teamipswich | 4:34.26 |
| 3 | 21 | Lexie Goodman | 17 | | Basildon Ph | 4:32.56 |
| 4 | 23 | Weronika Mikolajewska | 16 | | Co Cambridge | 4:31.97 |
| 5 | 22 | Cailin Hehir | 16 | | Watford SC | 4:32.27 |
| 6 | 20 | Ella Dawson | 16 | | Chelmsford | 4:33.74 |
| 7 | 18 | Erin Uttridge | 15 | | teamipswich | 4:34.26 |
| 8 | 16 | Ruby Chapman | 18 | | Norwich Swan | 4:35.73 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 25 | Jessica Keogh | 20 | | Hatfield | 4:30.75 |
| 2 | 27 | Ever Ives | 15 | | Hatfield | 4:26.08 |
| 3 | 29 | Sophie Dowding | 17 | | teamipswich | 4:25.09 |
| 4 | 32 | Cait Cotter | 17 | | Chelmsford | 4:15.00 |
| 5 | 30 | Jasmine Hall | 14 | | Basildon Ph | 4:23.90 |
| 6 | 28 | Annie McLeod | 16 | | Putteridge | 4:25.86 |
| 7 | 26 | Sadie Hunter | 16 | | Co Peterboro | 4:28.50 |
| 8 | 24 | Eva Lawson | 16 | | Berkhamsted | 4:30.90 |