No usually necessary, Willy. The only reason I can think of for paint to crack would be if there's a film of grease or dirt. As it's Artex, I guess it's been on there a few years. A film has most likely formed. The good old-fashioned way to deal with it is to scrub with Sugar Soap then two coats of emulsion.
Artex is fairly porous, so dilute the first coat with plenty of water to make sure it soaks in.