EVENT 233 Open/Male 400m IM - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 1 | Noah Bielby | 15 | Co Peterboro | 5:13.00 |
| 2 | 3 | Kian Ptolomey | 15 | Putteridge | 5:12.30 |
| 3 | 5 | Oliver Green | 16 | Co St Albans | 5:11.70 |
| 4 | 7 | Oliver Fenwick | 16 | Hatfield | 5:10.91 |
| 5 | 6 | Ramsey Gill | 16 | Co St Albans | 5:11.61 |
| 6 | 4 | George Everett | 16 | West Suffolk | 5:12.14 |
| 7 | 2 | Luca Baumslag-Grisi | 15 | Basildon Ph | 5:12.70 |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 9 | Lochlan Shaw | 15 | Flitwick | 5:08.73 |
| 2 | 11 | Ryan Wimpenny | 15 | Cheshunt | 5:08.15 |
| 3 | 13 | Stewart Butler | 15 | Dunstable | 5:05.90 |
| 4 | 15 | Riley Bashford | 19 | Deben | 5:04.53 |
| 5 | 14 | Harry Bird | 16 | Putteridge | 5:05.01 |
| 6 | 12 | Alexander Pattison | 15 | West Norfolk | 5:07.50 |
| 7 | 10 | Philip Spalding | 15 | Putteridge | 5:08.47 |
| 8 | 8 | Jeremy Brailsford | 16 | Witham Dolph | 5:10.04 |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 17 | Harvey Isle | 20 | West Norfolk | 5:02.92 |
| 2 | 19 | Luke Owens | 15 | Putteridge | 5:01.00 |
| 3 | 21 | Ashton Blake | 16 | Basildon Ph | 4:56.44 |
| 4 | 23 | Theodore Monk | 17 | Co Cambridge | 4:55.70 |
| 5 | 22 | B Macdonald-Williams | 17 | Bishop Stort | 4:56.06 |
| 6 | 20 | George Heather | 15 | Co Peterboro | 4:58.74 |
| 7 | 18 | Daniel Meier | 18 | Biggleswade | 5:01.56 |
| 8 | 16 | Alexander Ball | 18 | Potters Bar | 5:03.30 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 25 | Oliver Fuller | 15 | Co Cambridge | 4:54.91 |
| 2 | 27 | Daniel Thompson | 18 | Thurrock | 4:53.00 |
| 3 | 29 | Rafael Corliano | 15 | Co Cambridge | 4:51.87 |
| 4 | 31 | Daniel Williams | 17 | Hatfield | 4:50.29 |
| 5 | 30 | Joshua Jones | 16 | West Norfolk | 4:51.28 |
| 6 | 28 | Danylo Kravchenko | 16 | New Hall | 4:52.84 |
| 7 | 26 | Finlay German | 16 | Co Cambridge | 4:54.71 |
| 8 | 24 | Tyler Stone | 15 | Co Norwich | 4:55.20 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 33 | Daniel De Filippo | 16 | Flitwick | 4:49.42 |
| 2 | 35 | Csanad Rehus | 16 | Co Peterboro | 4:48.20 |
| 3 | 37 | Kian Lee | 17 | Co Peterboro | 4:46.52 |
| 4 | 39 | Kieran Ng | 15 | Co Peterboro | 4:42.96 |
| 5 | 38 | Robert Fenner | 17 | Basildon Ph | 4:45.02 |
| 6 | 36 | Patryk Nowak | 15 | Co Peterboro | 4:48.20 |
| 7 | 34 | Conor Mint | 16 | Basildon Ph | 4:48.80 |
| 8 | 32 | Jake Lloyd | 30 | Bishop Stort | 4:50.07 |
| Heat Number - 6 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 41 | Jacob Bacon | 15 | Co Peterboro | 4:42.46 |
| 2 | 43 | Samuel Jeffrey | 18 | Hatfield | 4:40.27 |
| 3 | 45 | Daniel McGuinness | 19 | Basildon Ph | 4:35.90 |
| 4 | 47 | Patch Robinson | 18 | teamipswich | 4:32.50 |
| 5 | 46 | Harrison Shaw | 18 | Flitwick | 4:35.44 |
| 6 | 44 | Reece Burns | 17 | Chelmsford | 4:37.79 |
| 7 | 42 | Lewis Jarrett | 19 | Thurrock | 4:40.61 |
| 8 | 40 | Frank Lamb | 16 | Co Peterboro | 4:42.81 |