There are plenty of books in which the heroine disguises herself as a man without anybody finding out. However, few of them convince me, as they usually just brush over the practical problems like going to toilet or menstruation. It might work for a few days – Tolkien threw in the darkness out of Mordor to help Éowyn get away with it – but I can’t really see it last for very long unless she has substantial help. For an example from real life take Jeanne Baré, the first woman to circumnavigate the globe, who traveled with her lover on a sailing ship disguised as a servant, but had their own cabin so she did not have to share the public head.
Having said that, one of my favourite authors, Gillian Bradshaw, has come up with a truly original solution to this problem in her book ‘The Beacon at Alexandria’. It’s set in the 4th century at a time when the Roman empire had already been divided into a western and an eastern half with each having its own emperor. Charis, the protagonist, is a young Greek noblewoman growing up in Ephesus (modern Turkey) who passionately wants to study at the famous medical school in Alexandria and become a physician. When her father threatens to force her into a distasteful marriage she enlists the help of her nurse and her brother to run away and comes up with a truly brilliant idea: she will disguise herself as a eunuch!
This explains both her feminine features and unusual modesty where bathing is concerned, yet gives her the freedom that at the time only a man could have. Only of course it doesn’t go quite as smoothly as Charis had imagined and invariably complications arise, some political, some emotional…
The author has an amazing knowledge both of the times and of medicine as it was practised then, which gives her world wonderful depth, yet what I like most about the story is the indomitable character of the heroine and the gripping plot. Unfortunately you can only buy the book second-hand, but it’s definitely worth hunting down!