A tyranny of the majority.

A tyranny of the majority (or tyranny of the masses) refers to an inherent weakness of direct democracy and majority rule in which the majority of an electorate can place its own interests above, and at the expense of, those in the minority. This results in oppression of minority groups comparable to that of a tyrant or despot.^{[1] So says Wikipedia.} 

‘First past the post’ political voting in the UK is a system guaranteed to disenfranchise large numbers of voters who choose not to cast their votes for one of the main political parties, so with the Greens, for instance, many thousands of voters spread across the country will rarely come together in sufficient numbers in one constituency to win a seat. The Green Party has one MP. The Liberal Democrats have nine, but over 100,000 members, almost the highest number in their history.  Of course it also means that UKIP and other extremist parties lose out on seats for which I am grateful, but you can't have it both ways.

An alternative system is called Proportional Representation. This is an electoral system in which the distribution of seats corresponds closely with the proportion of the total votes cast for each party. For example, if a party gained 40% of the total votes, a perfectly proportional system would allow them to gain 40% of the seats. All parties are therefore represented in Parliament, though successive attempts to move to this system have failed over the years and again only recently. 

A small overall majority is generally needed to form a viable government, sometimes achieved through a coalition with another party or parties. The ability of opposing parties to prevent legislation from being passed, following a debate, or the ruling party being forced to rethink or withdraw a bill is an important part of the checks and balances in our system of government. A massive majority gives the ruling party complete victory on every occasion, unless significant numbers of their own MP's vote against it or abstain. This is arguably unhealthy, although the House of Lords can vote against a bill and send it back to the House of Commons for another vote, though this usually only delays the inevitable. Some are even suggesting getting rid of the Lords which would remove an important part of the system, in place for centuries to mitigate the power of the Commons. A fully elected House of Lords would be a more justifiable reform.

With Brexit, Mrs May wants a big majority to stifle all opposition though it is likely to make no difference when it comes to actually negotiating with our EU partners, and they have said as much. We might be able to prevent a ‘Hard Brexit’ and perhaps stay in the Single Market or Customs Union if the opposition can muster sufficient votes. Who knows? God help us if Mrs May drags us out of the European Commission on Human Rights.

So, don't be tempted to vote with the perceived majority and give the Conservatives a landslide victory. This would be counterproductive and we may all live to regret it!