It was actually 37% of those who voted. Only two thirds of the electorate did, so in fact fewer than 1 in 4 of the electorate actually voted for the party that now has an absolute majority in the House of Commons.
That actually wasn't the biggest quantitative statistical unfairness of the night -- that award surely goes to the dramatic under-representation of UKIP and the Lib Dems in MPs compared to the popular vote they attracted -- but given the implications of an outright majority in Parliament, the disproportionate Tory representation is probably the most practically significant of the statistical anomalies that night.
That actually wasn't the biggest quantitative statistical unfairness of the night -- that award surely goes to the dramatic under-representation of UKIP and the Lib Dems in MPs compared to the popular vote they attracted -- but given the implications of an outright majority in Parliament, the disproportionate Tory representation is probably the most practically significant of the statistical anomalies that night.