BBC (ended 2005)
Alastair MacKenzie stared as Archie
what happened to his character
Archie left half way through series 5 with his sister to climb some mountains somewhere ( I can't remember which or where)
He then ended up in New Zealand where Lexie (Dawn Steele) went to join him.
He was never in the Series again after half way through Series 5, Lexie was in a few of Series 6.
Hope this helps