IF ENGLAND WIN
They will qualify for the last 16 as group winners by beating Slovakia.
IF ENGLAND DRAW
They will qualify and finish top unless Wales win, in which case the Three Lions will be runners-up.
IF ENGLAND LOSE
They will qualify in second place if Wales draw with Russia (England would be above Wales on their head-to-head record). If Wales win, though, then England will finish third. If Wales lose, then which of England and Russia finish second and third will depend on goal difference.
IF WALES WIN
They will qualify. They will finish top unless England also win, in which case Wales will end second.
IF WALES DRAW
They will qualify in second place unless Slovakia win, in which case they will finish third with four points.
IF WALES LOSE
They will finish bottom, unless Slovakia also lose to England, in which case they will finish third with three points.
If England finish third, they will have four points, which would give them a very good chance of progressing to the round of 16 as one of the four best third-placed teams. If Wales finish third, they will have gained either four points - or three, which would leave their chances on a knife edge.