Well done grandarog, spot on.
So this was the home of Sir Moses Montefiore, known as a Global campaigner for Jewish emancipation.The nearby Synagogue is still used and maintained, and contains the Mausoleum.
The main Tunnel was used by smugglers Horse and Carts, but was blown up and sealed.
The Caves where The Granville Caves. Nearby Wellington caves became HMS Fervent for WW2.
See attached photos from tthe 1935 Sales Brochure..............