This is a bit of a mystery. Clive writes:
I am reading a book written by Lewis Wilshire he writes about his walks in the countryside around Bath and Bristol, and he includes Kelston Round Hill. He states in the book as follows…It was here, on Kelston Round Hill that Sir John Harington built a castle, it was completed in 1591 in time for him to entertain the queen, on her royal tour of the west country. [the Queen being his godmother Elizabeth 1st]I have tried to find out more about this castle as he speaks as if it was actually on the clump, so I am hoping your records will enlighten me.I live at Hill Head near Portsmouth now but for 18yrs of my life i lived in a bungalow at the top of Saltford hill, with a wonderful view of Kelston and the clump.From time to time my friends and i would run from our homes up to the hill and back so it holds a lot of memories for me.Now i am trying to piece together its history.Hope you can give me a little more info
“Jacques”, the inventor of the flushing toilet, built a castle on the Clump? And Queen Elizabeth I stayed up there?? Is it possible??? Thanks Clive!
Kelston Roundhill and Roundhill Barn 
The author and academic Gerard Kilroy writes to say –
> On the ‘castle on the hill’, it is easy to be sure. Sir John Harington’s house was in the village, opposite Park Farm, but knocked down when Caesar Hawkins built the new house on the top of the hill nearer Bath, further to the east. Harington has a picture of the fountain it contained, and some think remnants of that survive in the present garden.
The Metamorphosis of Aiax, on which his reputation for invention of the water-closet rests, is a complex and arcane allegorical work, to which only a few select friends, like Thomas Markham and Lord Lumley, were given annotated explanations. The copies belonging to these two men survive in the Folger Shakespeare Library (Lumley), and Princeton University Library (Markham). The work, and his autograph annotations in those copies, make it clear that the real excrement in Elizabethan society was the system of torture and oppression of Catholics (like his cousin Markham) and Lumley, and the culprit named in the five surviving annotated copies (the other three are incomplete) is Richard Young, J.P., who arrested the young priest, William Harrington, in 1593, in the rooms of Henry Donne (younger brother of the poet): a man tortured and so brutally executed in 1594 that he was wrestling with the executioner trying to disembowel him on the scaffold. Young was responsible for throwing Henry Donne, after torturing him, into Newgate, where he died of the plague. He was only one year younger than John Donne. The diagram of the water closet, indeed the whole of the central section of the book, was written by Harington’s ‘secretary’, Thomas Combe, also responsible, significantly, for a book of emblems produced in 1593, three years earlier.
I have given a full account of this in two chapters on Harington in Edmund Campion: Memory and Transcription (2005), in my edition of the Epigrams of Sir John Harington (2009), and in a long article in ELR (2011), which carefully examines the manuscripts of this work, The Metamorphosis.
Sadly, the popular myth of Harington as a proto-plumber will probably persist, but it diminishes his real achievement, which was to survive at the heart of Elizabeth’s court, while being very critical of some of the real injustices of his time. As such, he could be regarded as a patron of toleration, and certainly as an advocate for religious unity, about which he felt passionately, as so many of the Epigrams show.