A Princess Runs Away by Barbara Cartland

The beautiful Princess Vasila, an orphan, who has been looked after by Baroness von Bergstein in a Grace and Favour house, is astonished when an Equerry arrives to take her to Windsor Castle to see the Queen.
She is not told until she arrives that Prince Gadelov of Saralovia, which is a small Balkan State, has appealed to Queen Victoria to give him a Royal British wife so that he can be protected from the grasping Russians.
When the Queen tells Vasila that she is to marry Prince Gadelov immediately, she is horrified and very frightened.
Without really thinking she runs away down a passage and out through a side door of The Castle. She then jumps into a parked van and its driver agrees to take her wherever she wants to go.
As they are leaving Windsor Castle, the van is stopped by Prince Gadelov arriving in an open carriage. When she sees the man who is to marry her, she knows that she would rather die than allow him to touch her.
The van driver puts her down at a nearby circus, as she loves circuses, and here she goes to look at the Helter-skelter, which she has never seen before.
As she wants one thing to remember in case she is taken back and married before she can prevent it, she asks a stranger who is standing by her to take her on the Helter-skelter.
The man is Kelvin Ridge, who has just arrived from India. He is in disguise because, having discovered a dastardly Russian plot to murder the Viceroy, his life is in danger.
How the two of them, who are both running away from danger, ride on the Helter-skelter and how Kelvin Ridge finds it difficult, as Vasila clings desperately to him, to be rid of her as she has nowhere to go.
How she saves his life and he inevitably falls in love with her is all told in this exciting romance by BARBARA CARTLAND.