The Excelsior Mine near Luckett, was a small affair that worked between 1873 and 1884 on far older workings and produced only 5 tons of tin ore.
The Excelsior Tunnel however was driven south-westward from Deerpark Wood towards the North Engine Shaft of Kit Hill Mine looking to to connect to this 660 feet below shaft collar and form the main drainage level and tap into the rich lodes of tin and copper of that mine.
Driving of the tunnel started in 1877 and continued on and off over the next 60 years until 1938 when it was finally given up, still about 310mts short of its objective after hitting the very hard granites of the base seams of the working. It is however almost 1km in length and dead straight and it is possible to see the portal from the far end of the working.
In 1959 it was the centre of project Military Atomic Energy Authority operation orpheus investigating the possibility of masking the seismic signal given out by underground nuclear tests. For the full history see here:[url]http://www.subbrit.org.uk/sb-sites/sites/e/excelsior_tunnel/index3.shtml[/url]