The lock up is one of four remaining in Hertfordshire. It was built in 1800 using materials gained from the demolition of a chapel in the North East corner of the chancel of St Mary’s Church Ashwell. It is a small square building with a slate pyramid roof, and with its original studded plank door in an oak frame, and a barred iron grille above.
The lock up was used by the village Constable to lock up people making a nuisance of themselves. After spending the night in the lock up they were taken to the Magistrates in Royston the following day.
The lock up fell out of use, largely due to the activities of one Amos Pammenter who, after being locked up and given ale from his friends through the grille by straw, managed to tunnel out under the door and went home to bed. The authorities decided that the lock up was no longer fit for purpose. It was used as a lock-up until the early years of the 20th century, and thereafter housed the parish fire engine, a two-wheeled cart, until 1939.