Upon completion in 1967, Spencer commissioned a further construction project in secret, which saw the building of an underground facility in the caverns under the estate. The actual construction was met by a number of delays right from the beginning, with Spencer insisting the construction firm hired be replaced with one he could personally recommend. Trevor himself was well known for his convention-breaking designs, such as labyrinthine floorplans and elaborate traps and locking mechanisms.
By the start of that year he hired the New York-based architect George Trevor, likely of Trevor & Chamberlain. The wealthy British aristocrat Lord Spencer first envisioned an American mansion sometime before 1962.
