Is this for a story?
Bear in mind that, usually, the person would have been born with that name so it's not just one that would sound good at a certain age.
And all three have strong British connections. I'd go for Robert, simply because I think it sounds better with the surname, but maybe try and think from the parents' point of view, or whoever named this character in the story (if this is for a story, sorry if it isn't). Which would they prefer? Maybe it was a grandfather's name or they liked stories of King Richard or Robert the Bruce or love Sir Robert Moore?