From Singapore Burning page 261:
In 1936,during Percival's first posting to Malaya,Penang had officially been declared a fortress,but in the years that followed the wish had never quite been fulfilled in fact.True,two batteries of 6-inch guns and searchlights now commanded the entrance to George Town's harbour,easily Malaya's best port.Yet these were its only fixed defences.There were virtually no anti-aircraft guns....