P and his D split up and P agreed to pay D £1 per week to look after the child (previously he paid a neighbour to do this) and “keep the child happ”, but ceased payments after D remarried. CA held that there was consideration and the contract was valid.
Denning LJ: A promise to perform an existing obligation (in this case caring for the child) is good consideration since it can still confer a benefit, since in this case the father is benefiting from not looking after the child himself.
This seems to contradict the rule that in general social arrangements do not give rise to contracts.