Really loved this episode, agree, such a shame that only one is left!
Travelledtheworld,
Petrushka used to be a common Russian family or between close friends diminutive of Peotr, but fell out of use in the modern times, probably mostly because the strongest association is with the puppet (as in Stravinsky's ballet if anyone knows)
From wiki about the puppet:
Although the Russian word "petrushka" has a homonym meaning "parsley," in this context the word is actually a hypocoristic (diminutive) for "Pyotr" (Пётр), which is Peter in Russian. However, the character has little or nothing in common with such stock characters as Petruccio or Pierrot. Petrushka is rather a Russian Punch or Pulcinella in character.
When the old Prince was dying, he called for Andrushka as well (as you would call a boy, child named Andrei, esp. tenderly and intimately, normally a shortening between family members, and addressed to someone much younger than yourself), and I wondered if British viewers understood that change of name...