Well given Johnson's record as London Mayor, where he failed to deliver on the vast majority of his promises, I wouldn't trust him to organize a piss up in a brewery, with written instructions and in bold writing.
--------------------------------------------------------------------
Her Majesty's Principal Secretary of State for Foreign and Commonwealth Affairs, often informally referred to as the Foreign Secretary, is a senior official as one of the Great Offices of State within Her Majesty's Government and head of the Foreign and Commonwealth Office. The office is a cabinet level position.
The Secretary of State's remit includes: relations with foreign countries, matters pertaining to the Commonwealth of Nations and the overseas territories in addition to the promotion of British interests abroad.[1]
The Foreign Secretary also has responsibility for the Secret Intelligence Service (MI6) and the Government Communications Headquarters (GCHQ), which are directly accountable to this person.
https://en.wikipedia.org/wiki/Secretary_of_State_for_Foreign_and_Commonwealth_Affairs