My 1930 2 speeder has a bayonet red key type. Hidden under the passenger seat since as standard in 1930, there is nothing to stop anyone turning things on, starting the car and driving off.
Has to be said, most folk are flummoxed by the controls but I fitted one anyway.
As far as a modern one is concerned, as stated above you must fit the type that puts a load on the alternator as well as having a separate ignition contact. Widely sold for motorsport so you'll have no difficulty finding one.
