In 1855, John Ramsbottom, later locomotive superintendent of the LNWR, described a new form of safety valve intended to improve reliability and especially to be tamper-resistant. A pair of plug valves were used, held down by a common spring-loaded lever between them with a single central spring. This lever was characteristically extended rearwards, often reaching into the cab on early locomotives. Rather than discouraging the use of the spring lever by the fireman, Ramsbottom's valve encouraged this. Rocking the lever freed up the valves alternately and checked that neither was sticking in its seat. Even if the fireman held the lever down and increased the force on the rear valve, there was a corresponding reduction of force on the forward valve.