[andrewaylett]

Look up the rules for `.ltd.uk` :).

Also, for that matter, .plc.uk, .ac.uk, .sch.uk, .nhs.uk, .police.uk and .gov.uk. All of them are available only to organisations that already exist in a particular context, and only with their 'real' name.

That doesn't prevent some collisions around characters that are legal in business names but not in DNS, of course, and it also doesn't mean that anyone actually uses the .ltd.uk and .plc.uk domains: I don't think I've actually ever seen one in the wild. I've seen all the others, though.