THIS half term one York venue wants youngsters to unleash their inner spy.

The Bar Convent in York wants children to discover more about the history of secret lemon juice letters and try their hand at writing their own at home by downloading a worksheet from their website and following our social media channels.

From as long ago as the seventh-century, lemon juice has been used as an invisible ink, undetectable from prying eyes until heated. This method has been used by spies, prisoners of war and, by Mary Ward, the founder of the religious order who established the Blossom Street convent.

Sister Ann, superior at the convent, said: “When it comes to sending secret messages from inside a prison, we might not expect a sixteenth-century nun would be an expert at it but our foundress, Mary Ward, never cared much for expectations.

“She was trying to pave the way for a new way to carry out God’s work, which meant working within local communities and educating women. Because this was highly unconventional, the Catholic church were not supportive and she was imprisoned by the Inquisition in 1631.

“However, she still found a way to communicate with her supporters in secret using an unusual item as invisible ink; a lemon.

“This half term we hope that you can have some fun at home with this activity, writing and uncovering secret messages and discovering a bit of our history too.”

Click here to find out more.