simpson helmets are legal in the uk.
i got stopped with a bandit on, and just as the smart arse plod wanted to give me a ticket i pointed out the e4 badge under the chinstrap meaning it conforms to eu road use regulations and unless i was mistaken britain was still in the eu therfore eu law applies. he made a call and promptly siad have a nice day sir and ride carefully.
so i gave him a cheery wave going past on my back wheel at 90 ( i made that bit up)
the older 80's bandits are illegal but contary to popular belief you dont need a kite mark (that just means it meets british standards) take a look at any car tyre none will have kite marks but they will be e4 stamped meaning they are european road legal. or we could pull every frenchie who drove off the ferry.... now thats an idea