Opens with the quote, "O, from this time forth, my thoughts be bloody or be nothing worth." This is from Shakespeare's Hamlet.
The "Royal" Kenneth is identified as Kenneth Bowes-Lyon. Bowes-Lyon was the name of Queen Elizabeth the Queen Mother.
The hotel penthouse hosting The Royals is numbered 422. This is probably part of the episode-number running gag of the show, incorporating the episode numbers in the actual episodes, being episode 22 in season 4.
The more obvious reference to the episode number is the address of the King's gated compound at 422 Mountain Estate Drive. The other is Kenneth's hotel room 422.
At 17:22, the last name on the driver's license of "Prince Kenneth" is actually that of HM Queen Elizabeth the Queen Mother (QE2's and HRH The Princess Margaret, Countess of Snowdon's mother).