On Thursday at 2pm GMT, the football matches for group H of the World Cup 2018 will begin. By 4 pm GMT, the fate of that group will be decided.
Let us assume that Japan comes first and Colombia comes second (not an unlikely outcome, actually), both hence qualifying for the second round. Now, at 6pm GMT, the matches of group G begin. Belgium and England are already qualified for the next round, but they play against each other in order to decide who goes first, and thus, to decide whom are they to play in the next round.
Now, under the reasonable assumption that Colombia is a better team than Japan (which is the case in terms of both Fifa ranking and world cup experience), you would expect Belgium and England would like to play Japan in the next round. Not only this, but coming second of the group will mean avoiding Brasil, Argentina, Uruguay, Portugal, and/or France in the next rounds up to the final. In the other side of the qualifications, the only big teams are Spain and Croatia. As such, there is a huge incentive for Belgium and England to come second of the group.
Now, the only certain way for a team to come second is to lose the match (they are tied in everything else, and qualifying position might depend on a Fair Play ranking, which changes during their match anyway).
This scenario is quite strange. It is not that both directly benefit (and thus put effort) in a draw, but quite the opposite: they benefit from a defeat! Thus, you could imagine both putting no effort, or playing only with substitutes, or even, if they remain in a tie, to score an own-goal in the last minute of extra-time! I would imagine that all this is perfectly legal, but is it? Can a team be investigated for this behaviour? Presumably, football rules are tailored to foster competitive behaviour, i.e. to foster a win. Perhaps there are rules against evident own-goals to induce defeat?