"Dear President Cameron.
My brother-in-law was the former Nigerian minister for scientific space research and told me just before his sudden mysterious death of top secret results of astronomic survey showing big diamonds lying all over the solid gold pavements of Jupiter. My country's space research is well advanced towards building rocket to Jupiter but the true objective of the mission is being kept secret from everyone except you. Sadly we are low on funding and urgently need additional moneys to continue development of the rocket.
If you are willing to send us just £ one billion in used notes in a brown paper parcel in strict confidence I will be able to guarantee you share of these diamonds and gold worth many time lot more than £ 419 billions. This a a genuine offer not scamming at all in any way really at all. I assure I am man of complete honesty.
Please be sending us the money express soon and not to our neighbour country Bongo-Bongo Land who are wankers who will just waste it on unproductive Western luxuries like food and roads and schools and water supplies, instead of getting real not-at-all imaginary untold wealth from outer space.
I wish you God blessing my dear friend and I look forward to receiving all your money extra soon."