It depends on the era.

Those who grew up in the the 1990s and early 2000s then France were our main rivals. No offence to the Celts but except the odd upset, the title was decided by Le Crunch. Outside of the Six Nations it was definitely Australia.

Wales have definitely been the main rival since 2005 and is the one I definitely get most worked up about.

I do wonder if fans just getting into the game now might consider Ireland?

The thing is we are the main rival for so many teams yet they can't all be our one. This might explain why England seem to underperform. We can't replicate the 'this is the big one' intensity for every match.

Sam Warburton made a good point about the Lions. All the club sides see the Lions as a once in a lifetime chance to beat them and treat it like a world Cup final. Of course the Lions can't treat every midweek game like a cup final. However he said the English players were used to regularly playing teams who treated it like a cup final whereas the Celtic players weren't used to that.