There are numerous PODs for this, but what would have happened if by the time of the 1959 general election, the only candidates for Parliament standing using the "Liberal" label were, effectively and understood to be, Tory candidates (some Tory candidates continued to call themselves "National Liberal" until the late 1960s, but were not thought to be anything other than Tories).
I think this would have produced a Conservative victory in 1964, and then the butterflies go on from there.