Just did a quote and for comparison I did one including the Mrs as a named driver, it was £100 cheaper than just me alone, why would that be? we both have clean licence and no accidents.
Because females are deemed a lower risk by insurers. If a lower risk driver uses the car for at least part of the time that a higher risk risk driver would otherwise be using it the overall risk is reduced, ergo lower premium.
I see, I only did it out of curiosity, she is unlikely to drive my car anyway, she says it's too big and she'll hit things! So now she can drive it, much more chance of a claim in this case and I save £100!