Ninety-year-old Isobel Brown had no clue about how brilliant at crosswords she was until quite late in life.

But she has certainly been making up for lost time since Inspector Morse writer Colin Dexter put the idea into her head while watching a cricket match Mrs Brown, of Warneford Road, simply cannot stop winning The Oxford Times crossword — in fact, she has won £650 worth of book tokens in prizes over the last five years.

Last week, she decided to use 26 of the the £25 OUP tokens she has won by completing our crossword to treat her grandson Rupert Winchester to the multi-volume OUP Encyclopaedia of Popular Music.

Mrs Brown, who lives with her daughter, Judy Winchester, said she took up The Oxford Times crossword to keep her mind active, after retiring as a welfare officer for the blind at Oxfordshire County Council. She helped blind people in the county from 1953 to 1982 and her work was later recognised when she received an MBE.

Mrs Brown recalled her chat with the famous Oxford detective writer while sitting on the boundary to watch one of her grandsons play cricket.

“He just happened to be sitting next to me. I remember him saying, ‘are you interested in crossword puzzles? They are a good way to keep one’s mind occupied’. He is right.”

Mr Dexter, like his most famous character, is himself a celebrated crossword enthusiast and, for many years, compiled The Oxford Times crossword.

Mrs Brown said she had been saving up her prizes to buy her grandson something special.

“When I started winning, I thought that I was not going to be able to read all these books at my age. So, when I offered them to Rupert, he was thrilled.”

A love of words clearly runs in the family.

Mr Winchester works as a journalist with Reuters in London and previously worked at OUP. He also assisted helped his father Simon Winchester to produce The Meaning of Everything: The Story of the Oxford English Dictionary.

Mr Winchester said: “My grandmother seems to have been winning for five or six years now. I think she has won about 30 times. It is really very impressive for a lady aged 90.”