| Ansvar Insurance | | |
| Antares Managing Agency Ltd | 020 7959 1900 | 21 Lime Street, London, EC3M 7HB |
| Arch Insurance (UK) Limited | 020 7621 4500 | 6th Floor, Plantation Place South, 60 Great Tower Street, London, EC3R 5AZ |
| Argenta Syndicate Management Ltd | | |
| Argo Managing Agency Ltd | | |
| ArgoGlobal SE | 0207 712 7558 | ArgoGlobal SE, Aragon House, Dragonara Road, St Julian's, STJ 3140, Malta, ZZ9 9ZZ |
| Armour Risk Management Ltd | | |
| Ascot Underwriting Ltd | | |
| Aspen Insurance UK Limited | 020 7184 8000 | 30 Fenchurch Street, London , EC3M 3BD, United Kingdom |
| Aspen Managing Agency Ltd | | |
