EVENT 209 Open/Male 400m Freestyle - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 2 | 1 | Jacob Dessoy | 17 | S8 | Thurrock | 6:18.66 |
| 3 | 3 | Jacob Schultz | 14 | | Co Cambridge | 4:27.60 |
| 4 | 5 | Ryan Wimpenny | 15 | | Cheshunt | 4:27.27 |
| 5 | 4 | Oliver Meier | 15 | | Biggleswade | 4:27.53 |
| 6 | 2 | Corey Hare | 19 | S14 | teamipswich | 4:31.63 |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 7 | Charlie Birdsall | 15 | | Co Cambridge | 4:26.25 |
| 2 | 9 | Marcus King | 17 | | Putteridge | 4:25.65 |
| 3 | 11 | Lochlan Shaw | 15 | | Flitwick | 4:25.33 |
| 4 | 13 | Benjamin Palmer | 14 | | Bishop Stort | 4:24.65 |
| 5 | 12 | Csanad Rehus | 16 | | Co Peterboro | 4:24.99 |
| 6 | 10 | Thomas Fenwick | 14 | | Hatfield | 4:25.50 |
| 7 | 8 | Janos Csepely | 14 | | teamipswich | 4:25.70 |
| 8 | 6 | Alfie Page | 16 | | Co Cambridge | 4:26.30 |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 15 | Oliver Fuller | 15 | | Co Cambridge | 4:23.61 |
| 2 | 17 | Perrin Ma | 14 | | Hatfield | 4:22.40 |
| 3 | 19 | Oliver Fenwick | 16 | | Hatfield | 4:19.80 |
| 4 | 21 | Xavier Zerban | 14 | | Biggleswade | 4:19.40 |
| 5 | 20 | Daniel Moyses | 19 | | Co Peterboro | 4:19.80 |
| 6 | 18 | Lucas Day | 16 | | Rochford | 4:22.00 |
| 7 | 16 | Isaac Buchan | 16 | | Co Norwich | 4:23.20 |
| 8 | 14 | Kian Ptolomey | 15 | | Putteridge | 4:24.50 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 23 | Ethan Knights | 14 | | teamipswich | 4:18.80 |
| 2 | 25 | B Macdonald-Williams | 17 | | Bishop Stort | 4:18.65 |
| 3 | 27 | Ethan Wallis | 15 | | Norwich Swan | 4:15.44 |
| 4 | 29 | George Carter | 17 | | Co Cambridge | 4:13.03 |
| 5 | 28 | Jamie Wilson | 16 | | West Norfolk | 4:15.04 |
| 6 | 26 | K-Ets Yah-Khai | 16 | | Hatfield | 4:16.24 |
| 7 | 24 | Luke Owens | 15 | | Putteridge | 4:18.80 |
| 8 | 22 | Will Riley | 16 | | teamipswich | 4:18.98 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 31 | Luke Martell | 19 | | Watford SC | 4:11.15 |
| 2 | 33 | Conor Mint | 16 | | Basildon Ph | 4:10.20 |
| 3 | 35 | Frank Lamb | 16 | | Co Peterboro | 4:05.67 |
| 4 | 37 | Alexander Volkovoy | 20 | | Co Cambridge | 3:53.70 |
| 5 | 36 | Daniel Belsey | 17 | | Hatfield | 4:01.08 |
| 6 | 34 | Robert Fenner | 17 | | Basildon Ph | 4:08.35 |
| 7 | 32 | Oscar Hunter | 16 | | Norwich Swan | 4:10.70 |
| 8 | 30 | Zak Fellows | 16 | | Co St Albans | 4:12.99 |