Good evening! It's Wales v Ireland and, well, let's let Abba explain...

Yes, whoever wins tonight will reach at least the world cup play offs. But it's not that simple. Strap in. A Welsh win and Serbia not beating Georgia at home will see Wales into the World Cup directly. A Serbian defeat by a couple of goals and a point for Wales will see the Welsh also into the tournament.

But oh no, there's more. An Irish win and a Serbian defeat will take Ireland into the World Cup. And if Serbia draw, a five goal victory margin for Ireland would win them the group. The only thing that's guaranteed, is that whoever loses in Cardiff tonight will have no chance of qualifying for the world cup.

You think we've finished with the permutations? You're wrong! A draw in Cardiff knocks Ireland out but Wales would finish second, and would be one of the best placed runners up if Croatia and Ukraine draw and score the same or less goals tonight as Wales. But there's even fucking more! If the Croatia and Wales draw and the Croats score 2 more goals than Wales score then Wales miss out.

But finally, and the outcome that would be the funniest. If Wales and Croatia both draw and Croatia score 1 more goal, so 0-0 in Cardiff and 1-1 for Croatia, then it comes down to the fair play record, which Croatia are currently ahead by three yellow cards. If that somehow ends up equal, then the final play off place will be decided by the drawing of lots. Got all that? Good.

Right then, let's look at the teams. And Wales first. Hal Robson-Kanu starts ahead of Sam Vokes in the only change from the Georgia game on Friday.

As for Ireland, well Shane Long pulled out this morning with a hip injury, but considering he hasn't scored in forever that may not be the worst thing.

If Croatia are winning and this game is level with 20 minutes to go we could be in for one of the most mental ends to a game ever. Which wouldn't be good for the collective heart-rate of the Welsh and the Irish. Speaking of which, has anyone out there supporting either side tonight got anything done all day, or has it just been blind panic all day?

The atmosphere is building, a giant Welsh flag is being passed around. The Irish fans are filtering in to one corner of the Cardiff City Stadium, one of the worst away ends around. Kick off is approaching.

The teams are in the tunnel, looking to a man, utterly terrified. And out they walk into an absolute din in Cardiff.