EVENT 102 Open/Male 400m Freestyle - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 1 | Noah BRAZEL-HAWKINS | 15 | Dunstable | |
| 2 | 3 | Bertrand HARRISON | 10 | Wycombe Dist | |
| 3 | 5 | Liam TWINING | 13 | Dunstable | |
| 4 | 7 | Alex KARAFIAT | 11 | Co Milton K | |
| 5 | 6 | Zachary LUDWELL | 13 | Dunstable | |
| 6 | 4 | Elijah UNSWORTH | 10 | Team Luton | |
| 7 | 2 | Nathaniel DOEDENS | 11 | Wycombe Dist | |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 9 | Cameron GEE | 11 | Wycombe Dist | |
| 2 | 11 | Theo MILNER | 13 | Biggleswade | 6:46.36 |
| 3 | 13 | Finley WOOLGAR | 10 | TigersJersey | 6:09.15 |
| 4 | 15 | Jacob CLARKE | 12 | Wycombe Dist | 6:04.74 |
| 5 | 14 | Jack LUXTON | 11 | Wycombe Dist | 6:08.40 |
| 6 | 12 | Isaac GREEN | 14 | Wycombe Dist | 6:10.40 |
| 7 | 10 | Haydn ELLIS | 10 | TigersJersey | 6:54.92 |
| 8 | 8 | Nicholas RADU | 11 | Co Milton K | |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 17 | Chester CURTIS | 12 | Bo Southend | 5:52.80 |
| 2 | 19 | Junsong LUO | 11 | Ealing | 5:47.09 |
| 3 | 21 | Theo RAWNSLEY | 10 | Harpenden | 5:43.06 |
| 4 | 23 | Alexander GEORGIEV | 12 | Co Milton K | 5:39.28 |
| 5 | 22 | Thomas ROBERTS | 11 | TigersJersey | 5:40.50 |
| 6 | 20 | Tyler LAVENDER | 12 | Team Luton | 5:43.10 |
| 7 | 41 | Fredrik STEEVES | 13 | Wycombe Dist | 5:51.00 |
| 8 | 16 | Alexandru ZAHARIA | 11 | Ealing | 6:02.40 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 25 | Filip BOCHENKO | 13 | Ealing | 5:10.38 |
| 2 | 27 | Adam MESSIS | 14 | Ealing | 5:02.34 |
| 3 | 29 | Henry TAYLOR | 15 | Biggleswade | 4:58.97 |
| 4 | 31 | Nathaniel NG | 15 | Ealing | 4:49.13 |
| 5 | 30 | Karim MADANI | 14 | Ealing | 4:57.00 |
| 6 | 28 | Dewi FORDYCE | 13 | Berkhamsted | 5:00.60 |
| 7 | 26 | Max POND | 13 | Bo Southend | 5:04.88 |
| 8 | 24 | Jonty ELLIS | 12 | TigersJersey | 5:24.49 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 33 | Joseph EMMS | 15 | Biggleswade | 4:37.30 |
| 2 | 35 | Jack CANHAM | 14 | Team Luton | 4:36.40 |
| 3 | 38 | Kacper NOWOSIELSKI | 14 | Ealing | 4:22.00 |
| 4 | 40 | Xavier ZERBAN | 15 | Biggleswade | 4:18.20 |
| 5 | 39 | Mihailo VUCKOVIC | 14 | Ealing | 4:21.90 |
| 6 | 36 | Stewart BUTLER | 15 | Dunstable | 4:28.99 |
| 7 | 34 | Hayden JOHNSON | 16 | Biggleswade | 4:36.70 |
| 8 | 32 | Samuel CHILDS | 13 | Berkhamsted | 4:45.56 |