I do own a half helmet ( DOT) which I bought in America and used to wear that on my solo Harley .
Not legal over here but the coppers leave you alone , they know your not some idiot young speed rider.
I do use it of I am going on the motor way but on local roads I don't.
Got to say I absolutely love it without an helmet on
especially this summer and the heat , guess I will be wearing it in the winter when I pop out on it