Mr Rees-Mogg is a Member of Parliament (and is known, mostly affectionately, as the Member for the Eighteenth Century). He has been recently elevated to the position of Leader of the House of Commons and Lord President of the Council.
In what way is Mr Rees-Mogg eccentric? There isn't room here to make a list, but let me just say that he admits cheerfully to having taken his nanny (that is, the lady paid to look after him when he was a child) on political canvassing expeditions. (Though I'm not sure that Mr Rees-Mogg would approve of the trip's being called an expedition as the ped in the middle of the word tends to imply that the journey was done on foot, and it's said (with how much truth I do not know) that he actually used his Daimler.)
Anyway, Mr Rees-Mogg has provided his new government department with a list of rules to be applied to official correspondence. Some of these rules are matters of taste, some of them are matters of convention; some of them logically justifiable, some of them aren't.
Here they are in full.