Didn't notice the "permanently". Best get a plumber in as the pipes serving the rad will have to be blanked off. Also you need to make sure that the installation was not done with the rads in "series". Some systems were done like that some years ago (can't for the life of me think why, but a friend discovered that in his house). This means taking one rad out effectively breaks the CH flow and your boiler will not be able to pump water round the remaining rads. It's very rare, but needs checking.