Substations were either solid core porcelain or composite insulIn the past, the main options for support insulators at air-insulated HVAC ators up to 245 kV. In addition, RTV coatings have at times been applied to solid core porcelain post insulators to improve their pollution performance. New developments have recently been made when it comes to gas or foam-filled hollow core composite insulators as well as larger core diameters on solid core composite insulators. Nevertheless, the requirements for EHV and UHV AC installations in terms of length, mechanical strength, permissible deflection, creepage distance, shed profile and pollution performance still present a challenge for all existing insulator technologies. Realizing the need for high strength as well as low deflection under loads for applications such as earthing switches, disconnectors, reactors and busbar supports, a program was launched to develop hybrid post insulators. The basic concept was to combine the known service experience reported for solid core porcelain posts with the proven pollution performance of insulators with silicone rubber housings. The challenge was to provide a reliable and cost-effective solution that combines the mechanical advantages of solid porcelain and the electrical advantages of silicone housings for high pollution requirements. Selected design tests as well as electrical and mechanical type tests were conducted according to relevant IEC standards for composite and ceramic insulators. In addition, a long-term field test was set-up to establish more confidence in the concept. This installation was energized at 145 kV AC in May 2012 at the Koeberg Insulator Pollution Test Station (KIPTS) in South Africa and has provided final qualification for the new product. In addition, 420 kV AC hybrid posts were chosen for trial installations across several applications. This INMR article from 2015, contributed by Gustav Gödel, summarized the experience developing, designing, manufacturing,