Sycorax Leader- "I can summon the armada and take this world by force."
The Doctor- "Well, yeah, you could. Yeah, you could do that, of course you could. But why? Look at these people: these human beings. Consider their potential. From the day they arrive on the planet, and blinking step into the sun. There is more to see than can ever be seen. More to do than - no, hold on... Sorry, that's the 'Lion King'. But the point still stands."
The Sycorax are an alien race, humanoid in shape, have an exoskeleton, are great with swords and electric whips, and use Roboforms as Pilot Fish, the Sycorax then following them like a shark hunting for prey. They also inspired William Shakespeare to name a character in a play after them (see The Tempest).
The Sycorax went to London on Christmas Day of 2006 on a starship called Fire Trap, using the signal from the Pilot Fish. They intercepted a probe that was meant to take photos of Mars and used it to communicate to the human race. Since the probe carried a vial of A positive blood, the Sycorax used their blood control mechanisms to bluff their way into power, the reason being that blood control is more popularly know as voo-doo magic.
The 10th Doctor, Rose Tyler, Mickey Smith, and Harriet Jones (Prime Minister) and an operative from UNIT were sent up to the Fire Star to negotiate with the Sycorax to leave the planet. That was when the Doctor, having finally awoken from a recent regeneration cycle, won a sword battle against the Sycorax leader and had the Sycorax leave Earth with a message to the entire universe, "It is defended."
The cache you are looking for is big enough for SWAG. There is no pen though, so bring your own.