Abstract: A liquid fuel filler cap provided with a valve assembly in a channel extending through said cap said valve assembly comprising means defining at least part of a channel, a valve seat in said channel, a valve member adapted to co-operate with said valve seat to seal said channel, and means to bias said valve member into engagement with said seat, said biasing means comprising a pivoted member comprising a first portion which is adapted to move said valve member, and a second portion, and means for engaging with said second portion and for imparting a turning moment to said pivoted member which is greater than and in the opposite sense to the turning moment imparted to the pivoted member by said valve member alone when the valve member moves away from the valve seat, said first portion and said second portion being on opposite sides of the point of pivotal support of said pivoted member.