Should I stuff it in my carry on back pack,put it in a hard rolly case for hold luggage or nestle in the bike bag ?

Carry on, or on your head as a hat.

Have always carried mine on. Never been questioned so far.

Just carry it on as it is. I’ve never had a problem doing that in 8 years.

Carry on it is,cheers for replies.

EasyJet once tried to charge my son and I an extra £20 each at the gate for our helmets as carry on, they said there was no room on the plane. Obviously I asked how £40 would make the plane bigger, then we put the helmets on still stood in the queue. 5 minutes later they said we could take them off and not pay extra.

Now that is genius Mr colp.Duly noted.