Hi,I'm Zoey and I'll be assisting you. I'm reviewing your question now. Please be patient while I compose a reply for you.
This is a scam, which we have seen many times before. First of all, Nigeria has no jurisdiction over crimes that were not committed in Nigeria, just as your country has no jurisdiction over crimes committed outside of the UK. You cannot be charged in the UK for an offense that was not committed in the UK.
Legally, speaking, the email you received is pure nonsense. This is just a way to frighten you into wiring money to Africa to avoid an arrest that can't possibly happen and to tempt you to try to collect $2.5 million USD that doesn't really exist.
Secondly, diplomatic couriers are not mailmen. They cannot be hired to carry anything to a private citizen. They are attached to embassies and consulates and their job is to carry sensitive, classified political documents from one ambassador to another. You would never be able to receive a parcel by a diplomatic courier, and embassies and consulates have nothing to do with the payment of awards, contest winnings, or inheritances.
By responding to your letter, you have done two things. The first is to let the scammers know that your email address is an active one. They send letters like yours out by the thousands every day and they only know that someone read it if you respond.
The second is that you have guaranteed that now you will get more scam offers of all kind, because you took the bait and your email address will be on a list of active people.
In short, there is no real money, no matter what they tell you in their reply. It's for you, because you fell for their email. And what will it cost you? Every penny you are willing to wire them to try to get your nonexistent millions. And they will take your last dime if you let them.
Cease all contact with them. They are liars and thieves. They are just phishing for your personal identifying information so that they can commit identity theft and are looking to steal all your savings besides.
Any unsolicited message with news from a stranger that is much too good to be true is a scam. You would never get official government news of this sort from an email.
Report the fraud to actionfraud.police.uk and have nothing further to do with them.
If you have since given them your passport and driver's license and personal data, take every possible precaution against identity theft.
Just checking in to see if you need more help or any clarification of my answer. If so, please reply here on this question thread.