Mel Giedroyc announced the winner as Birtwhistle, grandmother of eight, despite Richard Burr being a strong favourite for the title after his five-week run of being crowned star baker - a Bake Off record.
The shocked winner, dubbed queen of consistency, said: “I'm absolutely overwhelmed and pretty speechless and emotional. I couldn’t believe that I could win it.”
Mary Berry said she was proud of the second female winner of the show in a row. She said: “Nancy has the instinct. She loves baking and she is a perfectionist and to win the GBBO final that’s what you have to be.”
Paul Hollywood said: “I think it worked beautifully for her I think she absolutely nailed it in the final.”
Her apple kites were given ‘top marks for flavour’ by judge Mary Berry, and she came first in the technical challenge after she perfected the three classic recipes.
Luis Troyano, 43, also missed out on the Bake Off title.
The two judges said that, for once, they were in total agreement about who should win.
2012 winner of the show, John Whaite tipped Birtwhistle to win earlier this week. He told The Guardian: “Nancy is so consistent and she never gets flustered - I think those are the two characteristics that are most important.
"Remaining calm under pressure is not easy - particularly when you are being televised. So it's Nancy for me.”
This year’s series has hit the headlines with one of the most controversial stories yet to stem from Bake Off, in which two contestants left the show as a result of #bingate.
Iain Watters was booted off the show when he threw his baked Alaska in the bin after Diana Beard removed it temporarily from the freezer. She left the show on her own accord, reportedly due to ‘illness’.
Nancy Birtwhistle has five children and eight grandchildren. Born in Hull but now a Lincolnshire resident, the 60-year-old retired GP practice manager loves to bake for her family, and does so to reduce costs.
She has been known to teach her hairdresser how to bake, and gets recipe inspiration from a French chef whom she met in France when she and her husband Tim renovated a house there.