Coleshill House was the seat of the Playdell-Bouveries and was built in 1660, possibly designed by Inigo Jones. The design was influenced by the Queen’s House in Greenwich. Situated as it was on high ground with extensive views, water supply was a problem for the estate.
In 1770 these water supply problems were eased by the construction of an underground tunnel network. This network intercepted a well on the far side of a nearby road and led down to the house, gathering extra water from underground springs on the way. This supply tunnel terminated in a large cistern adjacent to the house and an overflow led down a second tunnel, probably at one time to the garden.
Sub Brit was given permission to enter and document the tunnels in June 2011 by the National Trust, the current site owners. This was a joint project with the Coleshill Auxiliary Research Team. The supply tunnel to the north was found to be 166 metres long and had several changes of direction. It included two side tunnels, of lengths 25 and 7 metres. Near the end of the tunnel a large well shaft rises from the tunnel, approximately 14 metres deep. This well is particularly interesting as it has steel rods forming a crude ladder up the inside of the stonework. It is believed that these were installed by the Auxiliary Units who trained on site during World War II. A second shaft along the course of this tunnel was probably used for construction access.
The south or overflow tunnel was 140 metres long and proceeded pretty well in a straight line although a slight change in direction may mark the meeting point of two separate excavations. Occasional recesses (for candles or lamps during construction?) were recorded. At around 110 metres a shaft is entered and it is possible that the final distance from here to the end was constructed by cut and cover as the height of the tunnel here is a mere 0.5 metres, versus 1 metre at its start. The tunnel is lined in brick throughout. There is a connection to the original cellars of Coleshill House from the water tunnels and these too were entered and recorded.
Ironically despite the efforts made to establish a water supply, Coleshill House burnt down in 1952 and was subsequently demolished. The site of the house is marked on the surface with hedging.