I've just found your message from March last year and have signed up to Roots.com so I could send you an answer.
I have just been looking at the history of my old prep school, Gadebridge Park, Hemel Hempstead. I was there in the 1950s and remember Hinwick House being on the school honours board, shown against names from earlier times. My searching led me to
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www.bedfordshire-lha.org.uk/newsletters/HIB%205,9.pdf> from which I quote . . .
"Augustus Henry Orlebar was the Flight Commander of the Schneider Trophy team from 1929 to 1931, when Great Britain won the trophy outright. He was born on 17 February 1896 in the Red Room at Hinwick House, and was known in the family as ‘Harry’. His father was Augustus Scobell Orlebar, and his mother’s maiden name was Hester Mary Knowle.
Harry’s father had rented Hinwick House from his cousin Richard Orlebar, and ran a preparatory school there, which used the Orlebar coat of arms (argent, two bars gules with three roses argent) as the school crest.
The school later moved to Hertfordshire, where it was known as Gaybridge (sic) Park School; it continued to use the Orlebar crest, and periodically paid the family a royalty for so doing."
Another source states that Gadebridge House, formerly a private house, became a school in 1914 so this would be when it moved from Hinwick House. Gadebridge Park School was forced to move from Hemel Hempstead in 1963 when the New Town Commission took over the land. It is now Westbrook Hay School at Boxmoor.
Hope all this is of interest to you