It's one of the most fascinating chapters in the centuries-long history of Wentworth Woodhouse.
From 1949 until 1974, the grand stately home near Rotherham - one of the most gilded houses of its age - was given a new name; Lady Mabel College of Physical Education.
Lady Mabel was the sister of the 7th Earl Fitzwilliam and had grown up at Wentworth before the family hit financial troubles and were forced to find tenants for their ancestral mansion.
As the remaining Fitzwilliams retreated to a private apartment within the depths of the house, the staterooms and grounds came alive to the sounds of hundreds of young women training to be PE teachers.
Now, the house's owners, the Wentworth Woodhouse Preservation Trust, aim to honour the legacy of Lady Mabel's 'girls' by launching a new series of tours of the estate that focus on its 25 years as an all-female residential college.
The tours will cover parts of the house that have never before been seen by visitors, and will be led by a guide who studied at Lady Mabel and is a member of its active alumni association.
Sue Gravil arrived at Wentworth in 1967 and now volunteers at the house where she wishes she could 'stay forever'.
She will regale visitors with tales of student balls in the Marble Saloon and hockey matches on the front lawn, while showing them the converted areas of the house where the trainee teachers slept and ate.
Sue, now 70 and living in Lincolnshire, remembers arriving at Wentworth for a two-day interview shortly after England's football team won the World Cup.
"It was very impressive - the prospectus only showed the East Front, and as I turned the corner and saw the house it was a real 'wow' moment. I couldn't believe how big it was, and that there was another house behind it.
"When I started there in September, my mum borrowed a car to drive me from Grimsby and I remember unpacking my trunk in the pillared hall, which is now the reception area for visitors."
A keen netball player and athlete as a schoolgirl, Sue soon settled in, and was assigned a room in a former service area of the North Wing which she shared with a Welsh girl.
"The selection process was very clever - it wasn't just about who was the best hockey player, it was a mixture of people who could blend and who had empathy for the teaching profession."
Sue believes an iconic photograph of girls playing badminton in the Marble Saloon is 'overplayed' as it was only used briefly for games during the early years of the college's existence, but confirms that it was a dance studio when she was a student.
"When the college first moved in, it was the only practical indoor space available. The Whistlejacket Room was also used for dancing."
Most of the teaching took place in the old stable block, which became a gym with anatomy labs and classrooms for art and music - the students were required to study a second subject that they would be able to teach in future.
The front lawn was used for hockey, cricket and athletics, while tennis courts were located where the car park is now. Rounders and lacrosse were played on other pitches near a small building in the park used for feeding the deer herd.
"Most of my memories are of the friends I made - we were kindred spirits who really looked out for each other. Back then, women didn't have the vote until we were 21, so the staff were completely responsible for us."
Sue recalls Malory Towers-esque moments of mirth, such as the time when she was on 'front door duty' and an American tourist turned up late at night to ask where the golf course was. He actually meant the famous Wentworth Club in Surrey.
The cellars were converted into a common room and later a bar, and the girls were invited to men's colleges and even RAF bases for socials.
The highlights of the Lady Mabel calendar were the Christmas and summer balls in the Marble Saloon, the same room where King George V was entertained during a visit to Wentworth in 1912. Sue remembers that girls who did not have a male escort were not allowed to attend.
The Fitzwilliam family welcomed their new tenants, and Lady Mabel, by then married to an army officer and living near Sheffield, would often visit to dine with the students. The 9th Earl, Eric, was a reclusive bachelor, but he occasionally allowed groups of girls to tour the family apartments, where the Long Gallery was located. The 10th and last Earl spent most of his time at the family's Milton Hall estate near Peterborough, and came north only for the shooting season and racing at Doncaster.
After Sue left and began her teaching career, Lady Mabel College faded into the background of her life. It was only in 2000, when a chance acquaintance led to her hearing about the Old Students' Association, that she fell in love with Wentworth again.
In the 1990s, Sue and her husband decided to visit the house when it was between private owners - the Fitzwilliams had sold up in 1989, after the college's successors, Sheffield City Polytechnic University, ended their tenancy.
The parkland was still open to the public, but the house was in a lamentable state.
"One day we tried to go back and I was mortified. The grass was knee-high - the front lawn once had a cricket pitch that was said to be the finest in England, even better than Lord's. There was neglect and rubbish everywhere.
"I didn't go back inside the house until 2012, and since I became a volunteer I've been able to see just how far things have come.
"I love sharing my stories with people - not many people can say that they got to live here. Being at Wentworth is like coming home, I feel at peace with myself and that I belong here. It's where I would like to be forever."
One of the first people to book on the inaugural tour - which takes place on September 14, after which they will be held monthly - is Sybil Wilbraham, now 88, who was the first student to walk through the doors of Wentworth in 1950. Another old girl is travelling from the Channel Islands to attend.
"We will be touring unseen areas of the house. Plenty of ex-Lady Mabel students will be booking on, but they're open to everyone who is interested to find out more about student life there."
In 2020, the Lady Mabel College Old Students' Association will reach a significant milestone - the college's 70th anniversary - by going back to where it all started. After a long exile in the village pub, the Rockingham Arms, these high-achieving and pioneering women are returning to the house for their annual reunion at the invitation of Julie Kenny, the businesswoman who is chief executive of the Wentworth Woodhouse Preservation Trust who was herself taught at school by a former Lady Mabel student.
"That just shows how the house affects people," adds Sue.
The first of the Lady Mabel College tours at Wentworth Woodhouse is on September 14. Tours will run monthly and must be pre-booked. Visitors can also take part in separate tours of the staterooms, gardens and roof. There is a tearoom and gift shop. Click here to book.