EVENT 204 Mixed 800m Freestyle - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 2 | Marcus XU | 13 | Linslade | |
| 2 | 4 | Tia ELSEY | 11 | Linslade | |
| 3 | 6 | Shuhan YANG | 12 | Colchester | |
| 4 | 8 | Ella THOMAS | 11 | Linslade | |
| 5 | 7 | George RHODES | 14 | Team Luton | |
| 6 | 5 | Maisie GLASPER | 13 | Leighton Buz | |
| 7 | 3 | Lauren TOUGH | 14 | Team Luton | |
| 8 | 1 | Cole WEINTROP | 15 | Leighton Buz | |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 10 | Annabel WHETTON | 11 | Harpenden | |
| 2 | 12 | Jack MAY | 13 | Linslade | |
| 3 | 14 | Caroline SEDGWICK | 16 | Harpenden | |
| 4 | 16 | Tali FROOME | 14 | Harpenden | |
| 5 | 15 | Inaaya SAMPONG | 12 | Team Luton | |
| 6 | 13 | Jess CARTER | 15 | Bo Waltham F | |
| 7 | 11 | Kaylyn SAMPONG | 14 | Team Luton | |
| 8 | 9 | Thea SLATER | 13 | Team Luton | |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 18 | George STAMP | 13 | Linslade | |
| 2 | 20 | Zach CLIFFORD | 12 | Leighton Buz | 14:43.19 |
| 3 | 22 | Tommy DAVIES | 14 | Leighton Buz | 13:37.79 |
| 4 | 23 | Cora PAYNE | 10 | Bletchley | 13:20.14 |
| 5 | 56 | Katherine TOLAND | 11 | Flitwick | 13:32.90 |
| 6 | 21 | PHOEBE DOUGLAS | 12 | Bo Southend | 13:58.50 |
| 7 | 19 | Nora HUGHES | 11 | Colchester | |
| 8 | 17 | William WIGGINS | 15 | Leighton Buz | |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 25 | Sebastian MCCUSKER | 13 | Leighton Buz | 13:08.13 |
| 2 | 28 | Sophie GARLAND | 12 | Harpenden | 12:10.45 |
| 3 | 30 | Maximos RYAN | 12 | Ealing | 12:02.88 |
| 4 | 32 | Cassie BONNER | 10 | Epping For't | 11:30.00 |
| 5 | 31 | Megan MCKAY | 15 | Leighton Buz | 11:34.15 |
| 6 | 29 | David KANDELAKI | 13 | Linslade | 12:03.56 |
| 7 | 27 | Elizabeth STOCKS | 12 | Linslade | 12:21.50 |
| 8 | 24 | Eleanor WAHL | 11 | Leighton Buz | 13:18.51 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 34 | Henry CHALONER | 13 | Biggleswade | 11:21.20 |
| 2 | 57 | Willow BENTLEY-GREAVES | 15 | Hertford | 10:57.91 |
| 3 | 37 | Amy EDWARDS | 14 | Boldmere | 10:42.61 |
| 4 | 39 | Libby FLITTON | 12 | Dunstable | 10:39.20 |
| 5 | 38 | Adam MESSIS | 13 | Ealing | 10:39.30 |
| 6 | 36 | Lucia DAY | 13 | Team Luton | 10:57.45 |
| 7 | 35 | Freya BOOR | 14 | Biggleswade | 11:13.90 |
| 8 | 33 | Zara BELNIKOFF | 13 | Epping For't | 11:30.00 |
| Heat Number - 6 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 41 | Casper WHITTAKER | 12 | Biggleswade | 10:38.20 |
| 2 | 43 | Arthur WALKER | 14 | 4 Shires | 10:37.00 |
| 3 | 45 | Abigail TOMLINSON | 11 | Corby | 10:34.63 |
| 4 | 47 | Ayden ROUMILHAC | 13 | Willesden | 10:30.08 |
| 5 | 46 | Skylar GLENDENNING | 13 | Corby | 10:30.30 |
| 6 | 44 | Leo DOWDEN | 15 | Leighton Buz | 10:35.75 |
| 7 | 42 | Charlotte STOCKS | 12 | Linslade | 10:38.13 |
| 8 | 40 | Elizabeth GORE | 13 | Epping For't | 10:38.65 |
| Heat Number - 7 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 49 | Aaron RAWNSLEY | 13 | Harpenden | 10:16.96 |
| 2 | 51 | Evie ARMSTRONG | 12 | Dunstable | 10:08.70 |
| 3 | 53 | Lucy ALEXANDER | 15 | Harpenden | 10:02.72 |
| 4 | 55 | Lucy CHARLES-BARCLAY | 31 | Epping For't | 9:12.50 |
| 5 | 54 | Reece BARCLAY | 34 | Epping For't | 9:15.00 |
| 6 | 52 | Connie FLITTON | 14 | Dunstable | 10:05.80 |
| 7 | 50 | Jack CANHAM | 13 | Team Luton | 10:10.80 |
| 8 | 48 | Eliza JENNINGS | 13 | Biggleswade | 10:18.90 |