Not watched Ethel and Ernest yet, but I was a blubbering wreck when I watched What We Did on Our Holidays last year.
Oh god... Ethel & Ernest will have you in pieces.
It's sooo perfectly pitched, with a lovely understated English kind of sentimentality that steers the right side of cloying. At face value it's just the very ordinary story of two very ordinary people living very ordinary lives, but like all the best stories, it's all in the telling.
In many ways, the other Raymond Briggs story it reminds me of most is Fungus the Bogeyman - it's the way he captures the essential details of mundane domesticity, while all the big stuff is almost incidental.
It shows great restraint too. There's a detail about Raymond Briggs's own married life that is only briefly touched upon because it's outside the scope of this story. Including it in more detail might have ramped up the emotional impact but might have unbalanced it too - the narrow focus of the story is part of its strength.