I mean, the whole of the 5 series has been heading for the idea that Merlin and (benign) magic would triumph and Arthur would become 'the best king Camelot ever saw'- yet he pops his clogs at about 24! The BBC review called it 'his sacrifice'- well, what did he sacrifice? He didn't 'give himself' for the sake of his people any more than anyone else who die din that battle, did he?
I get the the whole Excalibur thing happens in 'the legend' though just about every tea shoppe west of Bristol has its own 'legends' about Arthurian legend, doesn't it? So why the death boat on the lake? The haven't exactly stuck true to the story to date- so why at the end? Leaving Camelot with a bereaved queen and still no guarantee that magic can again flourish!