Sybil has been playing the lottery every week since it first began in 1994. She buys four tickets two lucky dips and two with numbers of her family members' birthdays.
Last Saturday she bought the winning lucky dip ticket from Folly View Stores, in Faringdon, where one of her daughters lives.
Shop owner Moham-med Yaqub's son, Omar, 17, sold her the ticket.
Sybil said: "I told him to make sure it's a winner. It still hasn't sunk in."
Yesterday she thanked Mohammed in person and gave him a big hug.
He said: "Sybil is a very good customer and I'm thrilled for the family. You never expect this sort of thing to happen."
The couple went out on Saturday night so checked the numbers on Teletext the following morning. Sybil said: "George handed me the tickets from his pocket and I started checking them.
"I kept checking to make sure we really had all six numbers. It was unbelievable."
She then went to pick up her mother, Marri, 80, who lives in Uffington.
She said: "I rang Camelot and they confirmed we really had won. It's so amazing."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article