Mornington Crescent is notorious in English pop-culture for being a ruleless game, however that's mostly untrue. The game started out as having a ruleset while being played on some BBC radio show. The joke was that the audience was never explained the rules of the game, which led to a somewhat hilarious degradation and bastardisation of the rules.
Generally, when playing Mornington Crescent, some players are meant to collude and agree on the rules while newer/other players are left clueless.
On the other hand, you could just copy-paste one of the many rulesets pieced together from instances of the radio show and logic (?), and play it without that Mao taste.
On the third hand, you could play it as it was played on the later series of said show, as a humourous, rule lacking, tongue-in-cheek parody of over-complex games.