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Alice Tankerfelde (also known as 'Alice Wolfe') is known to have escaped from the Tower of London in 1543 while 'apparelled like a man'.
She had been tried by the Admiralty Court having been charged with two murders (since the murders occurred on water, the Admiralty Court had jurisdiction). Once found guilty, she was sentenced to hang on the piratesβ gallows at Wapping Old Stairs.
She was re-captured after her successful escape from the Tower following an encounter with the City watch. They 'became suspicious' of a woman dressed as a man (βa oman aparylyd lyck a manβ), and took her (together with her accomplice, John Bawde) into custody.
(See case 15 in Early, Erotic and Alien: Women Dressed as Men in Late Medieval London by J.M. Bennett and S McSheffrey; State Papers, National Archives reference SP 3/3, fols. 133-134)
She was subsequently returned to the Tower, and was eventually hanged together with her accomplice.
As an aside, another well-documented example of a cross-dressing escape from the Tower of London, although in this case a post-Medieval one, is that of William Maxwell, 5th Earl of Nithsdale, who was sentenced to death for his role in the 1715 Jacobite rising.
According to the contemporary account, his wife, Lady Nithsdale, visited his cell, accompanied by two acquaintances called Mrs Mills and Mrs Morgan (not her maid, as stated in the Wikipedia article). They dressed Nithsdale up in women's clothes, and an 'artificial headdress', then caked his face in so much make-up that it hid his beard.
Dressed like this, Nithsdale was able to simply walk out of the Tower, holding a handkerchief to his face, after which he fled to Rome.