EVENT 225 Open/Male 400m IM - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 3 | 1 | Luke Toland | 15 | Flitwick | 5:19.26 |
| 4 | 3 | Harry Rowson | 15 | Putteridge | 5:18.24 |
| 5 | 2 | Heath Harrison | 15 | Stowmarket | 5:18.50 |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 4 | Harvey Atkinson | 16 | Colchester | 5:14.96 |
| 2 | 6 | Jacob Jenkins | 16 | Norwich Swan | 5:11.83 |
| 3 | 8 | Hughey Sullivan | 16 | DunmowAtlant | 5:09.33 |
| 4 | 10 | Sebastian Turculet | 15 | Hemel Hemp | 5:06.03 |
| 5 | 9 | Chiu Ki Cheng | 15 | Co St Albans | 5:06.38 |
| 6 | 7 | Oliver Butt | 16 | Deben | 5:10.06 |
| 7 | 5 | Byron Miller | 15 | Colchester | 5:12.32 |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 12 | Thomas Fenwick | 15 | Hatfield | 5:05.14 |
| 2 | 14 | Lochlan Shaw | 16 | Flitwick | 5:03.51 |
| 3 | 16 | Jed Millin | 18 | Stowmarket | 5:01.90 |
| 4 | 18 | Jude Staton | 18 | Co Peterboro | 5:00.48 |
| 5 | 17 | William Hughes | 16 | Chelmsford | 5:01.00 |
| 6 | 15 | Joseph Subba | 15 | Co St Albans | 5:02.32 |
| 7 | 13 | George Everett | 17 | West Suffolk | 5:04.15 |
| 8 | 11 | Zachary Fraser | 16 | Co Peterboro | 5:05.45 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 20 | Oliver Fenwick | 17 | Hatfield | 4:58.44 |
| 2 | 22 | Ashton Blake | 17 | Basildon Ph | 4:55.10 |
| 3 | 24 | Alexander Pattison | 16 | West Norfolk | 4:54.00 |
| 4 | 26 | Philip Spalding | 16 | Putteridge | 4:51.02 |
| 5 | 25 | Kameron Baker | 15 | Co Peterboro | 4:52.70 |
| 6 | 23 | Finlay German | 17 | Co Cambridge | 4:54.71 |
| 7 | 21 | Zachary Piscopo | 15 | Co Peterboro | 4:56.28 |
| 8 | 19 | Ivan Ijomoni | 15 | Thurrock | 4:58.60 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 28 | George Heather | 16 | Co Peterboro | 4:50.00 |
| 2 | 30 | Joshua Jones | 17 | West Norfolk | 4:48.22 |
| 3 | 32 | Luke Owens | 16 | Putteridge | 4:47.02 |
| 4 | 34 | Jamie Wilson | 17 | West Norfolk | 4:43.36 |
| 5 | 33 | Jacob Bacon | 16 | Co Peterboro | 4:45.41 |
| 6 | 31 | Daniel Thompson | 19 | Thurrock | 4:47.71 |
| 7 | 29 | Ben Howlett | 19 | Deben | 4:49.93 |
| 8 | 27 | Janos Csepely | 15 | teamipswich | 4:50.53 |
| Heat Number - 6 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 36 | Daniel Moyses | 20 | Co Peterboro | 4:40.84 |
| 2 | 38 | Kian Lee | 18 | Co Peterboro | 4:40.28 |
| 3 | 40 | Tyler Stone | 16 | Co Norwich | 4:35.22 |
| 4 | 42 | Frank Lamb | 17 | Co Peterboro | 4:29.02 |
| 5 | 41 | Harrison Shaw | 19 | Flitwick | 4:32.22 |
| 6 | 39 | Robert Fenner | 18 | Basildon Ph | 4:36.60 |
| 7 | 37 | Csanad Rehus | 17 | Co Peterboro | 4:40.78 |
| 8 | 35 | Lewis Jarrett | 20 | Co Norwich | 4:41.00 |