Please help. My adult cavalier and puppy cavalier persist in eating the others food. We've tried feeding at different times, different ends of the kitchen, sitting in the middle but at any chance they get they're eating the others food. I'm concerned about the problems this may cause with hyperactivity in the dogf and slow growth rate in the pup. Has anyone any suggestions on how to slove this!

i suggest that you lock one dog out in another room when you feed the other! its fairly straightforward really :) 
I would also suggest that you are quite strict at mealtimes....feed, then remove the bowl after they stop. On the whole it is not a good idea to leave dogs to "graze", and the pup needs ore frequent meals than the adult anyway. All the cavs I have known will eat for England, and have to have their food intake monitored closely.