Tyranny, according to my understanding of that word, has two aspects to its meaning. Firstly, it is a government where the separation of powers do not exist or is so futile as to prove little effect; secondly, the manner in which the laws are enforced in such a state.
The current socialist British Government have worked tirelessly to remove the remaining checks and balances of our system moreso than any before it. The laws they have proposed and often rammed through Parliament have not been in accord with liberty but with totalitarianism.
I believe our current Government is the greatest threat to our liberties than we have seen fro a long time. At present the Civil Contingencies Bill is going through passage to become law. It has been compared to the Enabling Act that granted Hitler his powers back in the 1930s. Attemps are being made to do away with trial by jury - a vital safeguard to liberty. We are being told we need permission to walk our own streets (ID cards), we have been traitorously ignored by the handing over of sovereignty to foreign powers (and the Executive throwing the just charges of treason brought by patriots out of the courts because the judicary and executive are not independent), the list goes on...
People should read what happened in 1930s Germany. It's a great lesson for our time, and would perhaps open the eyes of many to what is really going on.*
Dubhdara
* The following link may be of some use here, especially to US readers:
http://www.freedomforceinternational.org/freedomcontent.cfm?fuseaction=voicenazi&refpage=issues