I know Wales are capable, they've done in twice in recent times at Twickenham! But beating the host team WC in Twickers is a big ask, and I certainly would see it as an upset that early in the tournament.

Ditto. A full strength Samoa team can be pretty handy and Japan have traditionally lacked a powerful pack, despite recent improvements. Added to all of this, second place in Pool B is going to be hotly contested.