A £35m donation from billionaire inventor Sir James Dyson paved the way for the purchase of Holt Hall, it has been revealed.
The former outdoor learning centre was bought by private school Gresham's earlier this year, with plans now unveiled to turn it into a new prep school.
The school paid Norfolk County Council £4.25m for the Grade-II listed Victorian property and has now unveiled ambitious plans to renovate the site - which will be financed by its former pupil.
Sir James is the son of Alec Dyson, who was head of classics at the private school until he died at 43.
Following his death, former Gresham's headmaster Logie Bruce-Lockhart allowed Sir James and his brother to continue attending the school under a scholarship.
And the vacuum cleaner pioneer says his latest donation to the school is his way of showing that he is "forever grateful" for that decision.
Sir James said: "Holt Hall is a magnificent setting and when it came up for sale we had the extraordinary opportunity to rescue this Victorian hall to provide a setting for a new cutting-edge prep school for Gresham's pupils.
"As the son of a Gresham's teacher, I had the free run of Gresham's grounds and playing fields in the school holidays - but the arcadian park of Holt Hall was out of bounds."
The plans unveiled for the Holt Hall renovation include:
- A new mirrored building beside the hall
- High tech equipment with facilities for science, technology, engineering, arts and maths (STEAM)
- Restoration of the Holt Hall building to form the new school
- A field studies centre to provide outreach programmes for local schools and residential stays
Headmaster Douglas Robb said: "This is a once-in-a-generation opportunity to rescue Holt Hall and breathe new life into its grounds.
"We are enormously grateful for the generous donation of Sir James Dyson and the James Dyson Foundation."
Who is Sir James Dyson?
Sir James is best known as the inventor of the bagless vacuum cleaner and is one of the richest people in the UK.
He was born in Cromer in 1947 and was educated at Gresham's School - which he attended from 1956 to 1965.
This is not the first time he has made a significant investment in his former school.
He previously donated almost £19m to finance a new STEAM building on site.
The building opened in July last year and provided the school with new classrooms, laboratories, workshops and an auditorium.
During the EU referendum, Sir James was a supporter of Brexit which he said would harm the European Union more than Britain.
He was then criticised following the vote after he relocated his company's headquarters to Singapore.
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