I took the opportunity to try as many helmets as possible at the London Bike Show.
Even during (or should I say especially, as fit is even more critical) my motorbike days, I tended to find that helmets are designed for two basic head types - The narrow of cranium and the wider. I am the latter which meant I had an AGV/Shoei, rather than Arai/Suomi head. I could pretty much pick up any of the former of the right size and get comfortable, whilst the latter always squeezed the area above the ears, unless large enough to be a sloppy fit. I would have loved an Arai Giga, but I'd have been kidding myself.
And so it is with cycle helmets. It was not lost on my wife that the relatively budget
Giro* that fitted my head was called the Bishop [helmet] but I found both the Protone and Mojito were like slipping on an old glove, with nary a twist of the fastener to provide a light, secure and even pressure around my noggin.
That said, I can't see the need to immediately drop the best part of two tonne on a bonce potty, but I would say fit is important first and foremost. Try lots and then select the one you like the look of from that crop. Do NOT think that it will settle in and give a bit, because even if that is true in a tiny way, it won't feel like it at the end of a 3 hour plus ride. Just go into lots of shops and try them on. DO NOT buy on-line and rely on returning it to try others, because you won't get round to it.
Russell
*The peak pulls off (as does the velco it fits on) to reveal a perfectly normal road lid.