(1) | 49.54 | CBP | Fred Hake | (Herne Hill Harriers) | 1 FINAL | Kingsmeadow Stadium | 12 May 2024 |
(2) | 49.6 | CBP | David McKenzie | (Croydon Harriers) | 1 FINAL | Tooting Bec | 27 April 1986 |
| 49.6 | CBP | Stephen Mitchell | (Epsom & Ewell Harriers) | 1 FINAL | Croydon Arena | 15 May 1994 |
(4) | 49.7 | | Tim Eaton | (Mitcham & Sutton AC) | 1 FINAL | Sheerwater, Woking | 24 April 1988 |
(5) | 49.8y | CBP | Tony Collins | (Hercules AC) | 1 FINAL | Motspur Park | 21 May 1966 |
(6) | 49.9 | CBP | Dick Addison | (Belgrave Harriers) | 1 FINAL | Croydon Arena | 24 April 1983 |
| 49.90 | | Lolu Oluwole-Ojo | (Epsom & Ewell Harriers) | 1 FINAL | Kingsmeadow Stadium | 15 May 2011 |
(8) | 50.27 | | Memphis Ayoade | (Herne Hill Harriers) | 1 FINAL | Kingsmeadow Stadium | 12 May 2019 |
| 50.27 | | Samuel Mowa | (Blackheath & Bromley Harriers AC) | 1 FINAL | Kingsmeadow Stadium | 15 May 2022 |
(10) | 50.28 | | Jack Dickson | (Kingston AC & Polytechnic Harriers) | 2 FINAL | Kingsmeadow Stadium | 12 May 2019 |
| 50.28 | | Ryen Rennie | (Blackheath & Bromley Harriers AC) | 2 FINAL | Kingsmeadow Stadium | 12 May 2024 |
(12) | 50.3y | CBP | Graham Piggott | (Wallington County Grammar School) | 1 FINAL | Motspur Park | 3 June 1961 |
| 50.3 | CBP | David Mote | (Surrey AC) | 1 FINAL | Motspur Park | 15 May 1976 |
| 50.3 | | Gavin Dublin | (Croydon Harriers) | 1 FINAL | Croydon Arena | 14 May 2000 |
(15) | 50.34 | | Stefan Richards | (Epsom & Ewell Harriers) | 1 FINAL | Kingsmeadow Stadium | 10 May 2009 |
(16) | 50.38 | | George Munt | (Sutton & District AC) | 2 FINAL | Kingsmeadow Stadium | 15 May 2011 |
(17) | 50.4 | | Michael Carlile | (Croydon Harriers) | 2 FINAL | Croydon Arena | 24 April 1983 |
| 50.4 | | James Hilston | (Belgrave Harriers) | 1 FINAL | Croydon Arena | 13 May 1995 |
(19) | 50.43 | | Billy Truman | (Sutton & District AC) | 3 FINAL | Kingsmeadow Stadium | 12 May 2024 |
(20) | 50.48 | | Klaysen Kafuti | (Croydon Harriers) | 2 FINAL | Kingsmeadow Stadium | 15 May 2022 |
(21) | 50.51 | | Shaun Cooke | (Sutton & District AC) | 1 FINAL | Kingsmeadow Stadium | 26 May 2013 |
(22) | 50.6y | | David Marchese | (Surrey AC) | 2 FINAL | Motspur Park | 21 May 1966 |
(23) | 50.62 | | Tim Kuria | (Woking AC) | 1 FINAL | Kingsmeadow Stadium | 15 May 2005 |
(24) | 50.63 | | Ryan Thomas | (Epsom & Ewell Harriers) | 1 FINAL | Kingsmeadow Stadium | 12 May 2002 |
(25) | 50.66 | | Jonathan Osbourne | (Hercules Wimbledon AC) | 1 FINAL | Kingsmeadow Stadium | 9 May 2010 |
(26) | 50.7 | CBP | David Mote | (Surrey AC) | 1 HEAT 2 | Motspur Park | 13 May 1976 |
(27) | 50.73 | | Lawrence Dight | (Croydon Harriers) | 1 FINAL | Kingsmeadow Stadium | 16 May 2004 |
(28) | 50.8 | | David Simpson | (Croydon Harriers) | 1 FINAL | Sheerwater, Woking | 23 April 1989 |
| 50.8 | | Andrew Bilby | (Sutton & District AC) | 1 FINAL | Croydon Arena | 11 May 1996 |
| 50.8 | | Ryan Thomas | (Epsom & Ewell Harriers) | 1 FINAL | Kingsmeadow Stadium | 11 May 2003 |
(31) | 50.9 | | Eshref Hassan | (Belgrave Harriers) | 2 FINAL | Croydon Arena | 11 May 1996 |
(32) | 50.97 | | Zak Curran | (Windsor, Slough, Eton & Hounslow AC) | 2 FINAL | Kingsmeadow Stadium | 9 May 2010 |
| 50.97 | | Keeran Sriskandarajah | (Herne Hill Harriers) | 1 FINAL | Kingsmeadow Stadium | 14 May 2023 |
(34) | 51.0y | | John Greatrex | (Alleyn's School, Dulwich) | 1 FINAL | Motspur Park | 30 May 1964 |
(35) | 51.04 | | Lolu Oluwole-Ojo | (Epsom & Ewell Harriers) | 3 FINAL | Kingsmeadow Stadium | 9 May 2010 |
(36) | 51.05 | | Ethan Curran | (Crawley AC) | 3 FINAL | Kingsmeadow Stadium | 15 May 2022 |
(37) | 51.08 | | Tom Handley | (Camberley & District AC) | 1 HEAT 1 | Kingsmeadow Stadium | 13 May 2018 |
(38) | 51.1 | | John Gladwin | (Belgrave Harriers) | 1 FINAL | Motspur Park | 29 April 1979 |
(39) | 51.11 | | Sylvester Akpalara | (Herne Hill Harriers) | 4 FINAL | Kingsmeadow Stadium | 9 May 2010 |
(40) | 51.16 | | Lawrence Dight | (Croydon Harriers) | 2 FINAL | Kingsmeadow Stadium | 15 May 2005 |
(41) | 51.24 | | George Mears | (Guildford & Godalming AC) | 1 FINAL | Kingsmeadow Stadium | 14 May 2017 |
(42) | 51.27 | | George Mears | (Guildford & Godalming AC) | 1 FINAL | Kingsmeadow Stadium | 15 May 2016 |
| 51.27 | | Fred Hake | (Herne Hill Harriers) | 2 FINAL | Kingsmeadow Stadium | 14 May 2023 |
(44) | 51.28 | | George Rees | (Kingston AC & Polytechnic Harriers) | 2 HEAT 1 | Kingsmeadow Stadium | 13 May 2018 |
(45) | 51.29 | | Noah Ridgeon | (Sutton & District AC) | 4 FINAL | Kingsmeadow Stadium | 15 May 2022 |
(46) | 51.3y | | G Smith | (London AC) | 2 FINAL | Motspur Park | 3 June 1961 |
| 51.3 | | M Bloice | (Belgrave Harriers) | 1 FINAL | Motspur Park | 30 May 1970 |
| 51.3 | =CBP | C Baxter | (Camberley & District AC) | 1 FINAL | Motspur Park | 18 May 1974 |
| 51.3 | | G Field | (Hercules Wimbledon AC) | 2 FINAL | Motspur Park | 18 May 1974 |
| 51.3 | | James Hilston | (Belgrave Harriers) | 2 FINAL | Croydon Arena | 15 May 1994 |
|
50 performances of 51.30 or better. |