EVENT 601 Open/Male 400m Freestyle - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 2 | Riley Hamer | 15 | | Co Lincoln P | 4:39.01 |
| 2 | 4 | Henry Mason-Smith | 14 | | Repton | 4:37.06 |
| 3 | 6 | Dante Palmer | 13 | | Nova Cent'n | 4:35.92 |
| 4 | 8 | Wojciech Walach | 15 | | Corby | 4:35.41 |
| 5 | 7 | Theo Black | 15 | | Leic Sharks | 4:35.43 |
| 6 | 5 | Jack Hicks | 16 | | Lincoln Vulc | 4:37.05 |
| 7 | 3 | Elliott Ratcliffe | 15 | | Etwall | 4:37.70 |
| 8 | 1 | Max Davies | 18 | S8 | Worksop | 4:46.63 |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 10 | Kieran Lucy | 15 | | South Lincs | 4:34.29 |
| 2 | 12 | Arlo Hems Gillson | 14 | | Repton | 4:32.80 |
| 3 | 14 | Oliver Swaine | 15 | | Loughborough | 4:31.37 |
| 4 | 16 | Owen Johnson | 17 | S10 | Repton | 4:30.67 |
| 5 | 15 | George Howard | 13 | | Co Leicester | 4:31.16 |
| 6 | 13 | William Kite | 16 | | Louth | 4:31.38 |
| 7 | 11 | Victor Bramley-Howell | 15 | | Co Leicester | 4:33.02 |
| 8 | 9 | James Lee | 13 | | Derby Excel | 4:34.83 |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 18 | James Cash | 15 | | Deepings | 4:30.10 |
| 2 | 20 | Jacob Harness | 15 | | Bassetlaw SS | 4:28.50 |
| 3 | 22 | Reuben Meadows | 15 | | Bassetlaw SS | 4:27.52 |
| 4 | 24 | Danny Barron | 17 | | Etwall | 4:24.29 |
| 5 | 23 | Eddie Baron | 16 | | Nova Cent'n | 4:24.81 |
| 6 | 21 | Edward Gregory | 13 | | Repton | 4:28.10 |
| 7 | 19 | Flynn Clark | 14 | | Derby Excel | 4:29.53 |
| 8 | 17 | David Bielawski | 16 | | Northampton | 4:30.20 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 26 | Corey Butterell-Quanbr | 15 | | Bassetlaw SS | 4:23.19 |
| 2 | 28 | Riley Woodward | 16 | | Northampton | 4:22.50 |
| 3 | 30 | Finley Dare | 16 | | Corby | 4:21.27 |
| 4 | 32 | Finlay Bird | 15 | | Long Eaton | 4:18.90 |
| 5 | 31 | Harry Lucas | 15 | | Co Leicester | 4:19.68 |
| 6 | 29 | Henry Jones | 16 | | Chesterfield | 4:21.72 |
| 7 | 27 | Connor Allen | 18 | | Wellingboro | 4:23.08 |
| 8 | 25 | Isaac Ebanks | 15 | | Derby Excel | 4:24.01 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 34 | Laurenzio Ciolan | 15 | | Corby | 4:16.10 |
| 2 | 36 | Benjamin Mould | 20 | | Lboro Uni | 4:14.80 |
| 3 | 38 | David Coyle | 20 | | Nova Cent'n | 4:12.70 |
| 4 | 40 | Dylan Jamieson | 17 | | Derby Excel | 4:12.48 |
| 5 | 39 | David Bucur | 17 | | Worksop | 4:12.68 |
| 6 | 37 | Samuel Green | 15 | | Bassetlaw SS | 4:14.70 |
| 7 | 35 | William Oxley | 15 | | Co Leicester | 4:16.00 |
| 8 | 33 | Freddie Burdett | 15 | | Co Leicester | 4:16.79 |
| Heat Number - 6 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 42 | Carlos Sierra Villegas | 17 | | Chesterfield | 4:10.22 |
| 2 | 44 | Jack Bignell | 17 | | Northampton | 4:07.30 |
| 3 | 46 | Edun Rowe | 17 | | Northampton | 4:04.10 |
| 4 | 48 | Austyn Manley | 15 | | Repton | 3:58.05 |
| 5 | 47 | Alexander Lawrie | 18 | | Uni of Nott | 4:00.79 |
| 6 | 45 | Daniel Walker | 18 | | Nova Cent'n | 4:07.08 |
| 7 | 43 | Jacson Crabb | 14 | | Co Leicester | 4:09.90 |
| 8 | 41 | Sam Brylka | 16 | | Corby | 4:11.59 |