Wednesday 6 September 2017 18:33, UK
Northern Ireland are a step closer to reaching consecutive major tournaments for the first time after their 2-0 World Cup qualifying victory over Czech Republic on Monday.
Michael O'Neill's men are guaranteed second spot in Group C and are well placed to seal a play-off berth as they bid to reach the Russia finals.
England's victory over Slovakia means they are close to qualifying as group winners, but Wales, Scotland and the Republic of Ireland still have work to do and could yet be involved in a play-off scrap.
Here we explain the format and take a closer look at each country's chances...
After the group stage concludes on October 10, eight runners-up will be drawn into four pairings, with two-legged play-off ties set for November 9-11 and 12-14, 2017.
The away goals rule will be used to determine a winner of the ties if scores are level after the second leg - whether after 90 minutes or extra time - and four play-off winners will advance to Russia 2018.
But only eight of the nine teams who finish second are eligible for a play-off spot - meaning one team with the least points will miss out.
Results gained against the bottom-ranked sides in each group do not count in the final play-off standings.
FIFA have confirmed that teams will be seeded for the draw on October 17, with the top four teams according to the FIFA rankings in one pot for and the remaining four in another.
The teams currently in second place in the groups are Sweden (19th in the FIFA rankings), Portugal (6th), Northern Ireland (23rd), Wales (18th), Montenegro (52nd), Slovakia (22nd), Italy (12th), Bosnia (30th) and Iceland (20th).
The nine group winners qualify directly for the finals and the eight runners-up with the best record against the teams finishing first, third, fourth and fifth in their section go into the play-offs.
Either Northern Ireland or Germany will reach next summer's tournament as Group C winners, although the world champions remain firmly in the driving seat.
There is an outside chance Northern Ireland could finish top, and automatically qualify, but they would have to beat Germany and Norway in their remaining two qualifiers and hope Azerbaijan beat Joachim Low's side too.
As such, the play-offs look to be Northern Ireland's best route to a first World Cup appearance since 1986.
Based on current standings, O'Neill's men possess the second best points tally and are all-but nailed on to feature in the play-offs.
Consecutive World Cup qualifying victories over Lithuania and Malta, coupled with England's victory over Slovakia, has left Scotland with a fighting chance of reaching the finals for the first time in 20 years.
For Gordon Strachan's men it's simple; win the two remaining qualifiers at home to Slovakia and away to Slovenia and the Scots are guaranteed second spot in Group F.
As things stand that looks to be enough to secure a spot in the play-offs, with the two 'victories' leaving Scotland with a hypothetical tally of 14, after the points gained against whipping boys Malta have been removed.
Victories against Georgia and Republic of Ireland in their final two games would see them end qualifying with 20 points and barring any slip-ups by leaders Serbia, take second place in Group D.
However, with Chris Coleman's men have drawn five qualifiers so far, they currently sit bottom of the table that determines who will make the play-offs, albeit only on goal difference with Bosnia.
Defeat at home to Serbia on Tuesday night has seen Martin O'Neill's side slip out of the running for a play-off berth at just the wrong time.
However, victories in their last two fixtures - at home to Moldova and away at Wales - would see the Republic end up second in the Group D standings (again, barring an unlikely late collapse by Serbia).
And with the Republic having so far collected 10 points against their group rivals, except last-placed Moldova, that would leave them in with a good chance of competing in a two-legged play-off tie in October, and possibly securing a first World Cup appearance since 2002.
