It is thought that, deeply religious, she couldn't bear the world to know she had fallen pregnant out of wedlock and had two stillborn babies.
Instead, she hid the tiny bodies in a briefcase . . . keeping them there even when she moved house.
The secret was only revealed after her death at the age of 74 when relatives, clearing out her home in Audenshaw, Tameside, uncovered her half-century heartache.
Police were called to the maisonette where she lived with daughter Lucia Grime, 45, and Lucia's son James, 23.
Now James has broken the family's silence for the first time. He believes his grandmother gave birth to the children after falling pregnant outside of wedlock. The shame she felt - as a deeply religious woman - meant she never told relatives she was expecting.
And when the children were stillborn, she was simply unable to let go.
In an exclusive interview, James said: "I think she didn't know what to do.
"She was Church of England and a very religious woman and this was probably taboo then.
"There are so many questions that will never be answered. I'm just upset she was never able to tell anyone.
"We were never able to hug and comfort her. She was such a nice woman. She probably didn't want to burden anyone else and just kept it a secret."
James said he was cleaning at the house in Rowcon Close with his mother when she made the find.
He said: "For two years after [my grandmother] died, my mum slept on the settee because she couldn't bear to go upstairs near her room.
"One day, we decided to clean it out and decorate.
"All of a sudden, my mum said `What's this?' and I went over to have a look.
"She was holding a case that was in a black bag . . . it just looked like a pile of ash."
James said they spent three days wondering what to do before calling police.
"Then the circus began," he said. "People jumped to conclusions far too easily. They were making her out to be some kind of Harold Shipman. That wasn't her - she was no baby killer."
James said Margaret had eight children and 14 grandchildren. She married in 1948, but divorced two years later.
She then met an Italian man in 1958 and they were married in 1981. The bones were found with a newspaper dated November 1956.
James said the discovery placed huge strain on the family. He hopes DNA tests due to show if the babies belonged to Margaret will finally bring some peace.
Lucia still lives at the council-owned home on Rowcon Close and is hoping to move.
Police said they awaiting DNA results before deciding on any further action.
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