| Name | Company Number | Date Appointed | Rating |
|---|---|---|---|
| Croeso Systems Development Ltd | 02624610 | 20/04/2001 | Dissolved |
| Daniel Pipelines Ltd | 02640107 | 19/03/2001 | Dissolved |
| Dawnleigh Ltd | 02661354 | 21/03/2001 | Dissolved |
| Dwr Cymru (Properties) Ltd | 03310610 | 21/03/2001 | Dissolved |
| Hamdden Ltd | 02705531 | 21/03/2001 | Dissolved |
| Hyder Finance (1998) Ltd | FC021459 | 19/03/2001 | Dissolved |
| Hyder Finance (Holdings) Ltd | 03404913 | 19/03/2001 | Dissolved |
| Hyder Investments Overseas Holdings Ltd | 02958248 | 21/03/2001 | Dissolved |
| Hyder Overseas Investments Ltd | 02906578 | 20/02/2002 | Dissolved |
| Hyder Power Investments Ltd | 03405258 | 21/03/2001 | Dissolved |
| Hyder Property Developments Ltd | 04081160 | 20/02/2002 | Dissolved |
| Hyder Securities (Utilities) Ltd | 03310618 | 20/02/2002 | Dissolved |
| Hyder Services (Electricity) Ltd | 02624636 | 21/03/2001 | Dissolved |
| Hyder Services (Water) Ltd | 03116475 | 21/03/2001 | Dissolved |
| Hyder Utilities (Operations) Ltd | 03405264 | 21/03/2001 | Dissolved |
| Infralec Finance Ltd | 02817686 | 19/03/2001 | Dissolved |
| Infralec Financial Services Ltd | 02201425 | 19/03/2001 | Dissolved |
| Infralec Investments Ltd | 02624639 | 19/03/2001 | Dissolved |
| Infralec Telco Investments Ltd | 02837273 | 19/03/2001 | Dissolved |
| Lusis Ltd | 03049185 | 21/03/2001 | Dissolved |
| Pen Y Fan Properties (No. 2) Ltd | 02421859 | 21/03/2001 | Dissolved |
| Pen Y Fan Properties Ltd | 02805438 | 21/03/2001 | Dissolved |
| Southern Energy Investments | 03117354 | 29/05/2002 | Dissolved |
| Southern Energy Investments U K Plc | 03118397 | 29/05/2002 | Dissolved |
| Southern Energy Investments Uk Holdings Ltd | 03108637 | 29/05/2002 | Dissolved |
| St. Mellons Investments Ltd | 02212190 | 21/03/2001 | Dissolved |
| WELSH WATER INTERNATIONAL LIMITED | 02366589 | 21/03/2001 | Dissolved |
| Welsh Water Ltd | 03049158 | 21/05/2002 | Dissolved |
| Western Power Delivery Ltd | 03786093 | 29/05/2002 | Dissolved |
| Western Power Ltd | 03786089 | 29/05/2002 | Dissolved |
| Wpd Avonbank Ltd | 03786092 | 29/05/2002 | Dissolved |
| Name | Company Number | Date Appointed | Date Resigned | Rating |
|---|---|---|---|---|
| SOUTH WALES TPL INVESTMENTS LIMITED | 02579323 | 27/04/2005 | 21/04/2006 | Dissolved |