Removing a radiator - cap or join

[Spursnwagos]

If I remove a radiator from the system, do I just cap the inlet and outlet pipes or do the pipes need to be joined together for the system to flow?
The system is a solid fuel backboiler with vent / expansion tank in airing cupboard for radiators.
There are 5 radiators in the system, but we are planning to remove them one by one.

Thanks in advance.

 

[oldbuffer]

If its a one pipe system, join. If its a two pipe (normal these days) system, cap.