Totally agree with uktog. It’s a fun night where most people make an effort to wear something with white in/on it. My husband also wears beige trousers with a white polo or long sleeved shirt ( depending on the climate). I take white trousers, a sleeveless white and a long sleeved white top, both of which also look great with black trousers for dinner another night, as do the white trousers with a different coloured top. I definitely wouldn’t call it an elegant night, though certainly some guests do look elegant!