The baths were a small part of the Dicket Mead villa, which was originally built in the 3rd century AD.
The village of Welwyn has been described as being the site of a Romano-British settlement, where a Roman road crossed the river Mimram.
The full extent of the Dicket Mead villa was never fully excavated prior to the construction of the motorway, but the baths were only one of at least four buildings in total.
Eventually arrangements were made whereby a steel vault would be built over the top of the baths with an access tunnel for the public.
Once the vault was completed the motorway was built over the top of it, and the remains of the baths sit 9 metres below junction 6.