But that is a term used by scammers to make you think it's "official" but it's a way to con you out of money - mainly in fake lottery and fake inheritance scams
If your friend is not a diplomat or working at a government agency and the package is being sent to his office address, it's a scam. A diplomatic package is NEVER sent to a home address or any individual who is not a high level government employee
If your friend has sent money he's the victim of an elaborate scam and needs to contact the police as there is no package coming to her
The ONLY diplomatic packages coming out of the UK are those being sent from UK government ministries to their embassies/consulates/high commissions overseas and there is NO receipt of any kind