Lewis played Duncan as a child. Lewis had an accident when he fell down a ravine or something and was unseen in hospital for a while. I'm not sure of the exact time but I think Lewis was still playing the role in 1997 and when Christopher was still around which was till 1998. When Duncan returned from hospital...
Brendan took over the role of Duncan when he was about 12. Brendan last appeared in the role when Duncan appeared at Alf's 60th birthday party. That was the last we saw we saw of Duncan until...
Benedict took over the role in 2016 (I think.)