1. A flow controller comprising: a housing assembly defining an inlet port, an outlet port, and a main flow path extending between the inlet port and the outlet port; a restriction member arranged in the main flow path; a first valve assembly arranged to allow or prevent fluid flow along the main flow path; a second valve assembly arranged to allow or prevent fluid flow along the main flow path; a first regulator assembly arranged to operate the first valve assembly based on a differential pressure across the restriction member; and a second regulator assembly arranged to operate the second valve assembly based on the differential pressure across the restriction member.