Marina is reading the letter she thinks is from George. From behind she is holding with 1 hand, one hand to her mouth, from the front she is holding with 2 hands. as it switches back and forth, the she goes from hand to her mouth to back to 2 hands again.
When Marina is reading the letter she thinks is from George, she is reading with 2 hands. when it switches to her back view and Penelopes face, her left hand is over her mouth. It switches back to her face and she is holding with 2 hands again. When it switches back to Penelopes face and her back again, her left hand is over her mouth again.
No need for the Duke's coachman to fret about "setting a course" from Somerset House to the Opera (Covent Garden) in London. It's still only a five-to-ten minute walk today - both buildings are exactly where they were 200 years ago.
The couples are line dancing to Chopin's Waltz in A Minor. The show takes place in 1813, and Frederic Chopin was born in 1810. Highly unlikely he wrote it at age 3.