(1) | 47.60 | CBP | Martyn Rooney | (Croydon Harriers) | 1 FINAL | Kingsmeadow Stadium | 15 May 2004 |
(2) | 47.65 | | Martyn Rooney | (Croydon Harriers) | 1 FINAL | Kingsmeadow Stadium | 14 May 2005 |
(3) | 48.3 | CBP | Tim Eaton | (Mitcham & Sutton AC) | 1 FINAL | Croydon Arena | 20 May 1990 |
(4) | 48.4y | CBP | John Strachan | (Hercules AC) | 1 FINAL | Motspur Park | 30 May 1959 |
| 48.4 | CBP | Rod Milne | (Guildford & Godalming AC) | 1 FINAL | Motspur Park | 15 May 1976 |
(6) | 48.59 | | Ryan Thomas | (unattached) | 2 FINAL | Kingsmeadow Stadium | 14 May 2005 |
(7) | 48.6 | | Martin Gaston | (Hercules Wimbledon AC) | 2 FINAL | Croydon Arena | 20 May 1990 |
(8) | 48.61 | | Frederick Afrifa | (Crawley AC) | 1 FINAL | Kingsmeadow Stadium | 23 May 2015 |
(9) | 48.69 | | Ryan Thomas | (Epsom & Ewell Harriers) | 2 FINAL | Kingsmeadow Stadium | 15 May 2004 |
(10) | 48.72 | | Shaun Cooke | (Sutton & District AC) | 2 FINAL | Kingsmeadow Stadium | 23 May 2015 |
(11) | 48.8 | | Roy Dickens | (Shaftesbury Harriers) | 1 FINAL | Motspur Park | 17 May 1980 |
(12) | 48.9 | CBP | Rod Milne | (Guildford & Godalming AC) | 1 HEAT 1 | Motspur Park | 13 May 1976 |
(13) | 49.0y | | Nick Lovatt | (Whitgift School, Croydon) | 1 FINAL | Motspur Park | 29 May 1965 |
| 49.0 | | David Mote | (Surrey AC) | 1 FINAL | Motspur Park | 14 May 1977 |
(15) | 49.03 | | Gavin Dublin | (Croydon Harriers) | 1 FINAL | Kingsmeadow Stadium | 11 May 2002 |
| 49.03 | | Klaysen Kafuti | (Croydon Harriers) | 1 FINAL | Kingsmeadow Stadium | 13 May 2023 |
(17) | 49.07 | | Dedan Simmons | (Harrow AC) | 2 FINAL | Kingsmeadow Stadium | 11 May 2002 |
(18) | 49.1 | | Mark Clark | (Guildford & Godalming AC) | 1 FINAL | Motspur Park | 18 May 1974 |
(19) | 49.18 | | George Pittwood | (Walton AC) | 1 FINAL | Kingsmeadow Stadium | 11 May 2024 |
(20) | 49.2y | | W H Holland | (South London Harriers) | 2 FINAL | Motspur Park | 30 May 1959 |
| 49.2 | | David Simpson | (Croydon Harriers) | 1 FINAL | Croydon Arena | 18 May 1991 |
(22) | 49.30 | | George Pittwood | (Walton AC) | 1 HEAT 2 | Kingsmeadow Stadium | 11 May 2024 |
(23) | 49.31 | | Thomas Westerman | (Guildford & Godalming AC) | 1 FINAL | Kingsmeadow Stadium | 12 May 2018 |
(24) | 49.32 | | Keeran Sriskandarajah | (Herne Hill Harriers) | 2 FINAL | Kingsmeadow Stadium | 11 May 2024 |
(25) | 49.4 | | Roy Dickens | (Shaftesbury Harriers) | 1 HEAT 1 | Motspur Park | 12 May 1980 |
| 49.4 | | Michael Parper | (Belgrave Harriers) | 1 FINAL | Croydon Arena | 11 May 1996 |
| 49.40 | | Lolu Oluwole-Ojo | (Windsor, Slough, Eton & Hounslow AC) | 1 FINAL | Kingsmeadow Stadium | 12 May 2012 |
|
27 performances of 49.40 or better. |