Tyrants do not gain and keep power just by their own efforts - it requires a set of overwhelming circumstances that make their authority all but enevitable, often despite thier own actions. Tyrants come to power because it seems there could have been no other way.
Theresa May has been in government since the first days of the Conservative rule - first in coalition with the now defunct Liberal Democrat party from 2010, and then as a Conservative only administration since 2015. Before she bacame Prime Minister in 2016 (following David Camerons ignoble rush from office once his Brexit referendum went against him) she had been Home Secretary, one of the Great Offices of State.
As Home Secretary Theresa May had an long record of repeated failures on many projects but sometimes with an eventual success. For instance, taking many, many years and costing many millions of pounds to deport terrorist. Among some she had a reputatino for doing, very, very little and doing it very, very slowly - often put down to a 'control freak' streak of wanting to consider every single possibility and doing so personally.
Theresa May's most notable failure was on migration for which she was responsbile as Home Secretary. All through her tenure she made speeches saysing that migration to the UK was too high by orders of mangnitude (it was hundreds of thousands and should at most be tens of thousands), and on each occasion giving guarentees that she would fix the issue and had plans and tools in place. Of course on each occasion she failed to fix the issue, migration figures growing ever higher in just about every year she has been in government.
Her dishonesty is highlighted by her later admission that she could not control EU migration while the UK remained a member of the EU (so she had knowingly been lying when she promised to reduce the figures), but worse even the non-EU migration figures (of which she did have control) rose under her rule. So she lied about what she could do and then lied about what she actually did too as well. To compound this all, when the EU referendum was called she declared her support for remaining in the EU - so wanting to ensure that she never could control migation to the UK.
That Theresa May a plodding, single threaded operator who has failed and lied and wanted to remain in the EU, that she has become the Prime Minister to lead the UK out of the EU is a demonstration of the 'circumstances' I referred to at the start of this piece. Looked at without prejudice she would be one of the last people suited to this job, but somehow has taken it.
Other marks of her tyranical streak are given in relation her support for Big Governemnt Socialism and her position on Human Rights.
As the leader of the 'Conservative' party, she got plaudits for calling for Big Government intervention in social issues - the antithisis of everything that a Conservative would appear to want. That she could not only say this, but get her party cheering her for it is another demonstation of the 'cirucmstances' I referred to at the start.
For Theresa May's record on human rights, one demonstration is her 'snoopers charter', - It is to long to examine fully here (do a websearch for it) but it makes ISP's responsible for recording all of their uses intenet activity (your activity) and then gives just about every civil servant access to those records on demand - so don't go upsetting any state bod, they have access to it all. While such officiousness is more typically Conservative, the additional budern of the admin and its cost is not.
Also on human rights, and more seriously, Theresa May is planning on taking it upon herself to withdraw from the European Convention on Human Rights, and implement a British Bill of Rights. This is wrong headed on many levels - firstly the ECHR is designed to protect the public from an over-reaching government, clearly we cannot trust the government to protect us from itself - it would never consider its own actions wrong, so would never act against itself to protect us, this rules out the government writing any replacement and rules teh government out of administering any replacement. Secondly, the British way is not to give people rights/permission, it is for individuals to be free and for the Government to be restrained - a bill of rights should (like the American Constitution) set out what government is permitted to do (starting from an assumption of nothing), not what people are permitted to do, so banning anything not specifically permitted.
But despite all this Theresa May is riding high in the polls - she is more trusted (by quite a way) than any alternative - this is where Tyranny comes from.
An independent UK is at risk of being led by a leader as bad, nast, officious and authoritarian as De Valera was in taking on an indpendent southern Ireland, and the SNP would be taking on an independent Scotland.
Under Theresa May, tyranny awaits.