EVENT 102 Open/Male 400m Freestyle - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 2 | 2 | Maximilian PETRAVICH | 12 | Team Luton | |
| 3 | 4 | Finlay AUSTWICK | 10 | Flitwick | |
| 4 | 6 | Alexander ROCHOWSKI | 13 | Linslade | |
| 5 | 5 | Alidar KOZHAMZHAROV | 13 | Willesden | |
| 6 | 3 | Theo TSANG | 12 | Ealing | |
| 7 | 1 | Frankie FRANCIS | 15 | Harpenden | |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 8 | Elliott WHITEHEAD | 13 | Harpenden | |
| 2 | 11 | Elijah POWELL | 12 | Linslade | 7:25.23 |
| 3 | 13 | Arya ZOLFAGHARI | 12 | Epping For't | 6:06.69 |
| 4 | 15 | Maximos RYAN | 12 | Ealing | 5:56.61 |
| 5 | 14 | Lewis HALLAM | 12 | Harpenden | 6:02.90 |
| 6 | 12 | Filip BOCHENKO | 12 | Ealing | 6:40.46 |
| 7 | 10 | Tyler LAVENDER | 11 | Team Luton | |
| 8 | 7 | Leonn STARK | 10 | Team Luton | |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 17 | Marcus XU | 13 | Linslade | 5:51.64 |
| 2 | 19 | Luke TRULL | 13 | Dunstable | 5:34.80 |
| 3 | 21 | Karim MADANI | 13 | Ealing | 5:31.00 |
| 4 | 23 | Ben GORING-FARROW | 14 | Linslade | 5:24.20 |
| 5 | 22 | Nathaniel NG | 14 | Ealing | 5:28.64 |
| 6 | 20 | David KANDELAKI | 13 | Linslade | 5:31.89 |
| 7 | 18 | George DAVEY-CROUCH | 13 | Bo Southend | 5:39.65 |
| 8 | 16 | Samuel FALLAHNIA | 12 | Epping For't | 5:54.21 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 25 | Robert JAMES | 12 | Epping For't | 5:15.60 |
| 2 | 27 | Ayden ROUMILHAC | 13 | Willesden | 5:11.70 |
| 3 | 29 | Matthew HORTON | 15 | Dunstable | 5:09.13 |
| 4 | 32 | Jack CANHAM | 13 | Team Luton | 5:00.00 |
| 5 | 31 | Oscar RABENSTEIN TOBBA | 14 | Ealing | 5:04.83 |
| 6 | 28 | Adam MESSIS | 13 | Ealing | 5:10.23 |
| 7 | 26 | Alexander BELNIKOFF | 15 | Epping For't | 5:13.35 |
| 8 | 24 | Henry CHALONER | 13 | Biggleswade | 5:18.90 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 34 | Alexandru APOSTOL | 16 | Epping For't | 4:56.51 |
| 2 | 36 | Owain ROBERTS | 16 | Team Luton | 4:55.60 |
| 3 | 38 | Rhys THOMAS | 16 | Linslade | 4:43.41 |
| 4 | 40 | Liam BAUTISTA | 16 | Epping For't | 4:39.09 |
| 5 | 39 | Kacper NOWOSIELSKI | 13 | Ealing | 4:41.60 |
| 6 | 37 | Adithya BANGERA | 14 | Epping For't | 4:51.62 |
| 7 | 35 | Jack LEES | 12 | Epping For't | 4:56.20 |
| 8 | 33 | Aaron RAWNSLEY | 13 | Harpenden | 4:58.06 |