"I had a nightmare this week. The Bake Off tent was absolutely pitch black. There were spotlights on Brendan and James's desks. I was completely in the dark. I was shouting: 'Can you put the lights on?'"

John Whaite hadn't looked like a potential Bake Off winner for ages and had edged into the final as the underdog. His bright explanations of what he's doing have long made him the contestant you'd most want to have their own show, but a champion? Surely not.

In the last week of the competition, James Morton and Brendan Lynch suffered all the ups and downs and John again flew under the radar – until the result.

Before anyone had made much progress with their savoury pithiviers, we visited the three finalists at home and got an overwhelming torrent of new info. We met James's girlfriend, filmed before she knew how many TV viewers would quite like to take her place, and discovered Brendan is a Buddhist and has a much younger boyfriend. Mr Brendan made a cryptic remark about his baking success being "a sign of how much he's managed to overcome".

We visited John's mum's kitchen, where the banter between him, her and his sister implied that John has been living in a 23-year-long episode of Have I Got News for You. "We were all a size 10 before he started," said Mum. "I don't think you were born a size 10," John fired back.

"I think he's got a 33.33% chance of winning," John's sister said, adding that if he did triumph: "We can be really proud of him for the first time ever!"

After a lot of rolling and folding, not to mention enough butter to grease a jet engine, it was time to apply the puff-pastry lids. Brendan brazenly predicted his presentation would be superior to James's, before all three put their pithiviers in to cook. The programme's editing suggested Brendan had stood there stock still the whole time his was in the oven, baking it with his eyes.

This intensity paid off: Brendan's bottom was firm, his topping was golden and his filling tasty and balanced. Brendan had slammed down a marker and, as the extreme pressure of the tent on the final weekend started to bite, a little celebratory dance on the desks with his fists was the first sign that his measured cool might slip.

After further high praise for John, who mastered his rough puff thanks to some trademark forking, the judges came to James. A slice of his pithivier slumped sideways on Paul Hollywood's plate. "Oh no," said James, even before Paul's knife confirmed the pastry was underdone. Soggy bottom.

Judges in talent-show finals can sometimes be nice, because all the contestants by now are brilliant by definition, or nasty, because standards should be stratospheric. Paul and Mary went for nice when they saw tears in James's eyes: they praised his filling, but it was too late. James, who gets so much joy from baking he transmits that satisfaction through the TV screen, looked awfully deflated.

Brendan stayed bullish, boldly awarding himself "ten out of ten" for the first round and confidently starting round two. Fondant fancies: tiny, sweet things that are troughable in one bite, yet deceptively complicated. Sponge, plus marzipan, plus buttercream, plus fondant, plus chocolate drizzle. The contestants had been let off making the plastic tray, the box and those crinkly white waxy cases, but this was still a fiendish technical bake.

"Sponge and accuracy," said Brendan, "[are areas] I do have some skills in." He eyed James, talking with the calm, quiet menace of a villain in a two-part psychological crime drama.

James, however, was not yet beaten. With his sponge in the oven, he licked some icing sugar off his finger and started coolly prowling round his workstation. "Nothing to it, really." Yes! Rock 'n' roll, Marlon Brando, recipe-in-the-bin James was back!

Fondanting the fancies was up James's street too. He dunked his sponge in the icing with abandon, while Brendan insisted that a full dip wasn't required. One drippy failure later, Brendan was forced out of his compulsive neatness and was plunging his sponges too, ending up ladling pink stuff onto the cake, his hands and the worktop. "It's not my finest work is it?" he said, tetchily.

He was right. The judges had now switched from sympathetic to, in the blind tasting, brutal. Brendan's chocolate was a mess, his fondant had issues and, in the chilling words of Mary Berry, "The application of the buttercream is poor."

John had gone wrong too, convincing himself that the sponges had to be perfect cubes and throwing a quarter of his cake away to make this happen. The result: minuscule fancies. Mary was offended. There was a brief moment where it looked like she was going to vomit profoundly on them. It turned out she was bending to critique the buttercream.

Mary observed that the standard had been low all round - "Consider yourselves chastised," said Paul – but James had won and was back on track. They say it every week and it's usually true: it was all on the showstopper, a chiffon sponge expression of what 2012 meant to each man.

John chose a relatively unremarkable "heaven and hell" theme. Brendan explained that his cake would be in tribute to his efforts to reunite two sides of his family who hadn't spoken for three decades.

While we waited to see the cake that could possibly fulfil Brendan's brief, James agonisingly fell to pieces. He chose to make not one cake, but five: four representing the nations of the United Kingdom, and a fifth that was a sort of greatest hits of the other four.

It started to slip away when he dropped a tin of cake mix on the carpet. Then his Turkish delight stuck to his greaseproof as he ran short of time. "I don't know how to rectify this. It might be one step too far..."

Before the final, final judging, there was a heartstopping moment outside on the lawn, as we saw what has always lain behind Brendan's exactitude, pride and executive-level efficiency. "I think to achieve the title would be... an extraordinary endorsement of what I've achieved in my baking over the decades," he said, full of emotion, stopping for a long time in the middle to gather himself, and tailing off altogether at the end as the camera lingered and lingered. An illustration of why it's OK to become completely wrapped up in, even moved by, ordinary people in a baking contest? Right there.

Inside, a pornographic close-up of John's chocolate mirror icing announced that he'd aced it. The inside looked orgasmic. "That really works," said Paul after a theatrical pause that was fooling nobody.

Had John just made the series winner? Brendan looked on and gulped fearfully, before presenting his showstopper. From the outside it was uncharacteristically rustic and ramshackle, with haystacky almonds and gingerbread men of gaily assorted sizes. Once sliced, however, it was a spectacular, feathery, multi-layered cloud. "Oooooh!" ejaculated both Mel and Sue, involuntarily.

Everything about Brendan's last bake was superb – Mary and Paul even tested those gingerbread men. James was way behind. His five cakes were just five cakes, not a showstopping whole. Having pointed this out, Paul took a bite of the middle one, the United Kingdom: "It's welding my mouth together." James forlornly encouraged the judges to try Scotland instead, but you can't win the final with a back-up cake.

So was it John or Brendan? The episode had seemed to be all about Brendan, but before the announcement, Mary talked about how much better he was at bakes he could diligently rehearse at home, as opposed to technical bakes that were an impromptu test of cooking talent.

Finally the three men stood and waited for the result, two pairs of shorts and a sensible fleece. A name was shouted out. John had, from nowhere but quite deservedly, won.

Follow @jackseale

WIN A BAKE OFF BOOK!

Each week, readers of these reviews have had a chance to WIN a copy of the Bake Off book, How to Turn Everyday Bakes into Showstoppers by Linda Collister, normally priced £20.

For your last chance to enter, follow us @radiotimes and tweet, using the hashtag #gbbort, your best and funniest answer to this question: What has this year's Bake Off inspired you to do more of?

Entries by 12 noon on Friday 19 October, please.

Last week's WINNER: Caroline Ashton, with the answer: "A loveable retro male, with immaculate presentation and attention to detail, victory’s surely a cinch for Brendan Lynch."

Terms and conditions: promoter is Immediate Media; UK entrants 16yrs+ only; winner picked from all @RadioTimes followers who submit an answer before 12 noon BST, 19/10/12.