If the cycling is definately caused by the room thermostat, it's because the hallway is heating up too quickly and isn't reaching an equilibrium with heat gain vs heat loss. Have you tried isolating the radiator nearest to the room thermostat as you say there are two radiators in the hallway? Alternatively, turn the thermostat up to it's highest setting and see if the boiler still cycles as frequently. If it does, it's not the room thermostat causing the cycling.
The other reason could be that the boiler is shutting down on over temperature. If all of the other radiators in the house have thermostatic radiator valves (TRV's), it may be that there is insufficient heat loss from the one non TRV radiator for the boiler return to be cool enough, so the boiler switches itself off until the water cools down through heat loss. If this is the case, reduce the boiler flow temperature.