they're wearing soup bowls...note the extended rim for placing bread so it doesn't rest in the soup. 
Very keen observation. So the Brits built a dual-use head gear. One, to keep the sun out of their eyes. Two, soup bowl with bread supporting extension. I suppose a third, they used a tougher material so even some noob from the South of London or Wales will struggle to break the soup bowl/head gear.
All makes spectacular sense to me.
boo