Enid Blyton 
The Circus of Adventure [EPUB ebook] 

Who is the strange, pompous foreign boy Gustavus Barmilevo invited to the children’s home by Bill for the holidays? The children soon discover that he is a prince, named Aloysius Gramondie, and has enemies on his trail. The enemies want to overthrow his uncle, who is too strong a ruler for them, and place the prince on the throne as a puppet ruler. Jack and Kiki find themselves following the others, who are kidnapped and taken to the strange country of Tauri Hessia; but he finds help with a circus. Will Jack be able to rescue the others with the help of his new friends and decide the fate of an entire nation?