EVENT 102 Open/Male 400m Freestyle - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 2 | 2 | Andrei GHEORGHE | 12 | Newport Pag | |
| 3 | 4 | Daniel GUIMARAES | 11 | Team Luton | |
| 4 | 6 | Max HART | 10 | Verulam | |
| 5 | 5 | Veer TAKHER | 10 | Watford SC | |
| 6 | 3 | David KANDELAKI | 12 | Linslade | |
| 7 | 1 | Oscar MCKERN | 15 | Verulam | |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 8 | Henry CHALONER | 12 | Biggleswade | |
| 2 | 10 | William TURNER | 12 | Biggleswade | |
| 3 | 12 | Ellis GLANTZ | 9 | Putteridge | |
| 4 | 14 | Alexandru COTRO | 12 | Haringey | |
| 5 | 13 | Jacob EDGELL | 15 | Verulam | |
| 6 | 11 | George HEARN | 14 | Dunstable | |
| 7 | 9 | Luke GRIFFIN | 13 | Linslade | |
| 8 | 7 | Charlie CUNNINGHAM | 14 | Biggleswade | |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 16 | Franklin SHIELLS | 12 | Biggleswade | 6:42.90 |
| 2 | 18 | Harrison COPE | 11 | TigersJersey | 6:13.60 |
| 3 | 20 | Callum RICHARDS | 13 | Harpenden | 5:59.30 |
| 4 | 22 | Sam SMITH | 14 | Linslade | 5:55.30 |
| 5 | 21 | Cody BRIGDEN | 11 | Watford SC | 5:58.10 |
| 6 | 19 | Tom GILBERT | 12 | Watford SC | 6:05.60 |
| 7 | 17 | George CHURCH | 10 | TigersJersey | 6:25.80 |
| 8 | 15 | Bertie BRENNAN | 9 | TigersJersey | 6:51.50 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 24 | Ethan HUNTLEY | 12 | Team Luton | 5:44.10 |
| 2 | 26 | Ben GORING-FARROW | 13 | Linslade | 5:38.10 |
| 3 | 28 | Hugo HARLEY | 12 | Watford SC | 5:19.60 |
| 4 | 30 | Montgomery BREWSTER | 11 | Watford SC | 5:15.00 |
| 5 | 29 | Joseph BREWSTER | 14 | Watford SC | 5:17.50 |
| 6 | 27 | Riley MARTIN | 13 | Newport Pag | 5:26.10 |
| 7 | 25 | Noah PRESTON | 12 | TigersJersey | 5:38.40 |
| 8 | 23 | Aidan JARVIS | 11 | TigersJersey | 5:51.90 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 33 | Alexander GAYDON | 13 | Colchester | 4:51.20 |
| 2 | 35 | Constantine CALLIAFAS | 13 | Watford SC | 4:45.40 |
| 3 | 37 | FELIX AMDOR | 13 | Broomfield | 4:43.20 |
| 4 | 39 | Max WALTERS | 15 | Watford SC | 4:33.66 |
| 5 | 38 | Daniel DICK | 16 | Newport Pag | 4:40.70 |
| 6 | 36 | William HARRIS | 15 | Watford SC | 4:44.70 |
| 7 | 34 | Ethan DICK | 14 | Newport Pag | 4:48.40 |
| 8 | 31 | Christos ROUMELIOTIS | 14 | Newport Pag | 5:13.27 |