Illegal on a bike I think
What sort of question is that? Where have you been these lids have been made since before I was born
well how do they compare to aria and shoei then
You want a practical helmet go get an arai or shoei
Simpon is an iconic helmet that looks cool.
Alex they are legal if you buy the bike specific ones
http://www.visordown.com/forum/forummessages.asp?UTN=270738&URN=3&dt=4&srchdte=0&cp=1&v=1&sp=
for more (maybe informed) info
cheers 4 the link good info 
i think thats the alien 1 or 2
looks the ********georgous bikes on the kings road have a real cracking set of lids,simpson,bandit,roof,bell all american
For fit, comfort and safety get an Arai.
For bad fit, mild forehead pain and the odd pull from plod, but look well cool, get a Simpson :w00t:
zzzzzzzz… 
The wearing of a helmet, and the selling of a helmet are two different things in law.
It is legal to wear any helmet that fits. The law is incredibly unspecific - deliberate as when the law was written they didn’t want people to stop wearing the leather and pudding basin helmets they were already using.
However, the law on selling a helmet for motorcycle road use is very specific, and Simpson helmets cannot be legally sold for motorcycle use in the UK.
Ive heard looking left or gith also spins your head clean off your neck! :w00t:
there is a raod legal version.
the normal 1s have a very small visual hole etc, their made for racing.
there was a case a few yrs abck when a bloke got pulled on a bike with 1 (b4 the leagal 1 came out) he took it to court and argued that if they were good enough for drag racing etc which they are made for then they are safe, he won the case, lol.
is this the finishing touch to the streetfighter transformation???