A battery powered lamp unit in the form of an electric lamp integral with a compartment to contain at least one electric battery to power the lamp, or electrical circuit whereby the lamp is powered by the battery, and a tubular supporting container having an open end into which the electric lamp is insertable for support thereby with the container surrounding the compartment and the lamp projecting beyond the open end. Engageable elements on the unit and interior of the tubular container are arranged such that the elements engage one with another some distance within the container from the open end when the unit is inserted so as to prevent removal of the unit. The interengaged elements can be unlocked by a key which can be inserted into the tubular container.