When I later watched his second and last appearance during episode 4 season 2 "The Angel Of Death" I thought it was strange that he were supposed to look so changed after only one year. (yes I know the season was filmed during less time) so I looked up a few things.
It is not the same actor! I knew that it really unreasonable that Luke was supposed to change so much. I think it was quite unnecessary that they switched actor.
The younger Luke was played by Jonathan Readwin and the older was played by Christian Cooke. However I think that it looks really strange that Luke was supposed to change haircolor, skin color and body built during one year, as you can see in the Images.
Drop a comment of what you think!