To quote the sixth Doctor :
In all my travelling throughout the universe, I have battled against evil, against power-mad conspirators. I should have stayed here. The oldest civilisation: decadent, degenerate, and rotten to the core. Power-mad conspirators, Daleks, Sontarans, Cybermen - they're still in the nursery compared to us. Ten million years of absolute power. That's what it takes to be really corrupt.