I got this Best Lock Lego from Asda. It's supposed to be compatible with real Lego. The base is a real Lego base. Usually I wouldn't buy anything but real Lego but this had a person with each set and there are 5 sets shown in the pictures. There were also some really good accessories and tools and things so I took a risk. The pieces seem to lock together quite well really. The fences are a bit loose. I think for a child who wanted to play it would be a bit of a pain but for someone who just wants to model they're quite good.
