| (1) | 49.5 | | Croydon Harriers A | | 1 FINAL | Carshalton | 2 September 2023 |
| (2) | 50.0 | CBP | Croydon Harriers 'A' | | 1 FINAL | Tooting Bec | 26 April 1986 |
| (3) | 50.09 | | Herne Hill Harriers 'A' | | 1 FINAL | Carshalton | 3 September 2022 |
| (4) | 50.30 | | Sutton & District 'A' | | 1 FINAL | Carshalton | 13 September 2014 |
| (5) | 50.32 | | Herne Hill Harriers | | 1 FINAL | Carshalton | 9 September 2017 |
| (6) | 50.5 | CBP | Croydon Harriers 'A' | | 1 HEAT 1 | Tooting Bec | 26 April 1986 |
| (7) | 50.54 | | Herne Hill Harriers | | 1 HEAT 1 | Carshalton | 8 September 2018 |
| (8) | 50.57 | | Herne Hill Harriers | | 1 FINAL | Carshalton | 8 September 2018 |
| (9) | 50.58 | | Sutton & District 'A' | | 1 FINAL | Sutton Arena | 7 September 2013 |
| (10) | 50.69 | | Herne Hill Harriers | | 1 FINAL | Carshalton | 12 September 2015 |
| (11) | 50.76 | | Herne Hill Harriers 'A' | | 1 FINAL | Carshalton | 10 September 2016 |
| (12) | 51.01 | | Sutton & District AC A | | 2 FINAL | Carshalton | 12 September 2015 |
| (13) | 51.17 | | Herne Hill Harriers 'A' | | 1 HEAT 1 | Carshalton | 3 September 2022 |
| (14) | 51.20 | | Woking AC | | 1 FINAL | Carshalton | 7 September 2019 |
| (15) | 51.25 | | Kingston AC & Polytechnic Harriers | | 2 FINAL | Carshalton | 3 September 2022 |
| (16) | 51.38 | | Woking AC | | 3 FINAL | Carshalton | 12 September 2015 |
| | 51.38 | | Sutton & District AC 'A' | | 2 FINAL | Carshalton | 9 September 2017 |
| (18) | 51.4 | | Mitcham AC | | 1 FINAL | Carshalton | 10 June 1972 |
| | 51.4 | CBP | Mitcham AC 'A' | | 1 FINAL | Wimbledon Park | 20 April 1974 |
| | 51.4 | | Herne Hill Harriers | | 2 FINAL | Carshalton | 2 September 2023 |
| (21) | 51.41 | | Sutton & District AC 'A' | | 1 FINAL | Sutton Arena | 8 September 2012 |
| (22) | 51.43 | | Kingston AC & Polytechnic Harriers | | 2 FINAL | Carshalton | 8 September 2018 |
| (23) | 51.5 | | Mitcham & Sutton AC 'A' | | 1 FINAL | Tooting Bec | 25 April 1987 |
| | 51.5 | | Mitcham & Sutton AC 'A' | | 1 HEAT 2 | Tooting Bec | 25 April 1987 |
| | 51.5 | | Epsom & Ewell Harriers 'A' | | 1 HEAT 2 | Kingsmeadow Stadium | 13 September 1992 |
| | 51.5 | | Woking AC 'A' | | 3 FINAL | Carshalton | 2 September 2023 |
| (27) | 51.6 | CBP | Mitcham AC 'A' | | 1 HEAT 1 | Wimbledon Park | 20 April 1974 |
| (28) | 51.65 | | Kingston AC & Polytechnic Harriers | | 1 HEAT 2 | Carshalton | 3 September 2022 |
| (29) | 51.7 | | Croydon Harriers | | 1 FINAL | Sheerwater, Woking | 21 April 1990 |
| | 51.7 | | Croydon Harriers 'A' | | 1 FINAL | Kingsmeadow Stadium | 22 September 1991 |
| | 51.7 | | Epsom & Ewell Harriers 'A' | | 1 FINAL | Kingsmeadow Stadium | 13 September 1992 |
| (32) | 51.78 | | Epsom & Ewell Harriers | | 1 FINAL | Carshalton | 11 September 2021 |
| (33) | 51.79 | | Woking AC 'A' | | 2 FINAL | Carshalton | 10 September 2016 |
| (34) | 51.8 | | Mitcham AC 'A' | | 1 HEAT 1 | Motspur Park | 30 April 1977 |
| (35) | 51.88 | | Woking AC | | 3 FINAL | Carshalton | 8 September 2018 |
| (36) | 51.9y | | Croydon Harriers | | 1 FINAL | Ewell Court | 30 June 1968 |
| | 51.9 | | Selsonia Ladies AC | | 1 FINAL | Motspur Park | 28 April 1979 |
| | 51.9 | | Croydon Harriers 'A' | | 1 FINAL | Motspur Park | 26 April 1981 |
| | 51.90 | | Hercules Wimbledon AC 'A' | | 4 FINAL | Carshalton | 8 September 2018 |
| (40) | 51.91 | | Sutton & District AC 'A' | | 1 HEAT 2 | Carshalton | 8 September 2018 |
| (41) | 51.95 | | Kingston AC & Polytechnic Harriers | | 2 HEAT 2 | Carshalton | 8 September 2018 |
| (42) | 52.0y | | Mitcham AC | | HEATS | Wimbledon Park | 17 May 1969 |
| | 52.0 | | Mitcham AC | | 1 FINAL | Wimbledon Park | 14 April 1973 |
| | 52.0 | | Mitcham AC 'A' | | 1 FINAL | Motspur Park | 30 April 1977 |
| | 52.0 | | Epsom & Ewell H | | 2 FINAL | Motspur Park | 30 April 1977 |
| | 52.0 | | Selsonia Ladies AC | | 1 HEAT 1 | Motspur Park | 28 April 1979 |
| | 52.0 | | Camberley & District AC | | 2 FINAL | Sheerwater, Woking | 21 April 1990 |
| | 52.0 | | Kingston AC & Polytechnic Harriers | | 4 FINAL | Carshalton | 2 September 2023 |
| (49) | 52.01 | | Kingston AC & Polytechnic H 'A' | | 2 FINAL | Carshalton | 13 September 2014 |
| (50) | 52.1y | CBP | Mitcham AC | | - HEATS | Wimbledon Park | 26 May 1962 |
| | 52.1y | | Mitcham AC | | 1 FINAL | Wimbledon Park | 9 May 1970 |
| | 52.1 | | Croydon Harriers 'A' | | 1 HEAT 1 | Motspur Park | 26 April 1981 |
| | 52.1 | | Mitcham AC 'A' | | 1 HEAT 1 | Croydon Arena | 23 April 1983 |
| | 52.1 | | Mitcham AC 'A' | | 1 FINAL | Croydon Arena | 23 April 1983 |
| | 52.1 | | Mitcham & Sutton AC 'A' | | 2 FINAL | Tooting Bec | 26 April 1986 |
| |
| 55 performances of 52.10 or better. |
