Name the primary aircraft used for air-to-air refuelling in the RAF.

The primary aircraft used for air-to-air refueling in the RAF is the A330 Voyager. This aircraft is specifically designed to perform air-to-air refueling operations and has the capability to refuel various types of aircraft in the air, enhancing the operational range and endurance of RAF missions. The Voyager can be equipped with advanced refueling systems that allow for both hose-and-drogue and boom refueling methods, accommodating a diverse range of military aircraft.

The other aircraft listed, while they have their own roles within the RAF, do not primarily serve as air-to-air refueling platforms. For example, the A400M Atlas is primarily designed for tactical airlift and transport missions, the C-130 Hercules serves a similar role in tactical airlift and can perform some refueling missions, but is not the main platform for that purpose, and the Eurofighter Typhoon is a multirole combat aircraft intended for air superiority and ground attack rather than refueling operations.