To say Jo Wheatley’s life has changed since winning The Great British Bake Off in 2011 is an understatement. Back then, she was a housewife and mother who had left school at 16 with only three GCEs. Now, she’s just published her second baking book, holds regular cookery classes from her Essex home and rubs shoulders with celebrity cooks such as Gino D’Acampo and her heroine, Mary Berry.

‘I still wake up every day and pinch myself that this is all really happening,’ she tells me, as we sit at her kitchen table in Ongar, laden with the products of a morning’s baking. ‘I feel so lucky to have had this opportunity. I’ll be eternally grateful for the confidence it’s given me. It’s so nice to do something you love.’

I warm to Jo immediately – and not just because she has baked me honey madeleines with a chocolate dip and the most divine Eccles cakes I’ve ever tasted. She is friendly and unaffected, and chats away engagingly while I’m transported to home-baking heaven.

On the kitchen counter is an enticing seeded white loaf, also baked this morning. Her shelves are stacked with cake tins, mixers, flavoured oils, jars of sprinkles and cake decorations. Her cupboard bursts with flours, sugars, chocolate, crystallised fruits, orange essence, vanilla bean paste and countless other tempting ingredients. Baking really has become her life.

Jo’s love of baking began when she was around three years old. Her nan (who’s now 89 and still swims a mile every day) used to give Jo pastry off-cuts to bake. She remembers her auntie making party cakes with blue icing for boys and pink for girls. Baking for Jo is intrinsically linked with happy childhood memories.

Jo’s mum was a housewife and her dad drove a newspaper van. The family moved from London to Wanstead when she was 11. Jo went to Wanstead High School, but didn’t do well.

‘I just didn’t enjoy learning,’ she says. ‘I loved childcare, home economics and religious studies. But I only got GCEs in those subjects and left at 16 with no idea what I wanted to do.’

By 17, she was married to Richard and at 18 gave birth to the eldest of her three sons. For a while, she and Richard ran a pub in Loughton, but after that she stayed at home and cared for her three boys, Billy, now 25, Jesse, 23, and Dylan, 17. The younger two are still at home, but Billy now has a baby son called Harley, making 43-year-old Jo a young but devoted grandmother – Harley calls her ‘Nanny Cake’.

Jo has never regretted having a family so early. ‘I loved being a mum and looking after the family. I made a good circle of friends at my ante-natal group and we still meet up 26 years later. My old school friends were out partying, but I never envied them. I found satisfaction in making a nice home.’

The family moved to North Weald and then, nine years ago, to their rural bungalow near Ongar. ‘I love waking up and looking out on the countryside, and going for walks,’ she says. ‘Essex gets a bad press, but there are so many lovely places here. It’s beautiful.’

Baking was always central to her role as a home-maker, as well as her way of relaxing. ‘When the kids were small, running around like loonies, I used to shut myself in the kitchen and escape.’

As the boys grew up, she sometimes wished she could start a career, but her lack of qualifications and experience held her back. ‘I’d never really worked and couldn’t see how I could get a job. I didn’t even properly know how to use a computer. I used to think if I tapped something into it, I’d accidentally delete everyone’s files.’

Then, in the summer of 2010, a friend phoned to tell her about a new baking show she might enjoy watching. Jo happened to have her laptop beside her and searched for The Great British Bake Off. ‘There was a button to click if you fancied applying, so I pressed it on a whim. It turned out they were full for that year, but it asked if you wanted to be on next year’s waiting list, so I just clicked “yes”, without really thinking about it.’

Months later, she received an email asking if she was still interested in applying. She filled in a form, submitted recipes online – with some computer help from her sons – was interviewed over the phone and was finally invited for an interview.

‘At every stage I thought, “What’s the worst that can happen?” I genuinely didn’t think I’d be selected, but they told me if I came for interview I’d get to meet Mary Berry afterwards. The thought of meeting her was so exciting, I decided to give it a go!’

To her amazement, she was chosen to be one of 12 from 4,000 original applicants to take part in the show.

‘The first evening I met the other competitors, the guys were talking about the structure of bread and the mechanics of it and I felt totally out of my league,’ Jo says. ‘I never thought I was very intelligent, so I’d avoid conversations with people I thought were cleverer than me.’

But she did have faith in her ability to bake, and to add an original twist to classic recipes. An early favourite, she survived round after round, despite disasters like accidentally turning the oven to defrost when attempting to bake brandysnaps. ‘I ended up with brandy mush instead.’

Judges Mary Berry and Paul Hollywood, and presenters Mel Giedroyc and Sue Perkins, were all friendly and encouraging, and gradually her confidence grew. In breaks between filming she religiously practised her baking skills for the next round – one week, producing 500 trial macaroons. ‘I had to beg friends to take them away!’

When it came to the final, she was still convinced she had no chance of winning, so relaxed. ‘I just thought, “I’ve done the whole journey now. I’m just going to have fun”.’

She produced a trio of mini Victoria sponge sandwiches, banoffee pies and meringues, beautifully presented in a flower-filled stand she’d found at TK Maxx. ‘Mary said my Victoria sponge was one of the finest she’d ever tasted,’ says Jo proudly. ‘When they announced I’d won, it really didn’t register. I only realised when I saw my boys jumping up and down.’

Her win made her an instant celebrity and she soon became used to well-wishers stopping her while shopping in Epping or Harlow. Having taught herself to overcome her fear of computers, she started a blog – Jo’s Blue Aga – which today attracts up to 30,000 followers. On it, she runs baking competitions, supplies recipes and cooking tips, and advertises her twice-monthly cookery classes.

She’s been holding one cupcake and one multibake class a month, but both fill up almost as soon as they’re advertised. They’re relaxed, informal affairs.

‘We start off in the conservatory and chat so everyone gets to know each other,’ she says. ‘We start baking at 10.30am, stop for lunch and a glass of wine, and finish off afterwards. Some students have never baked before while others are more competent. I’ve had a couple come down from Scotland and one lady who came all the way from Australia.’

Her first book, A Passion for Baking, became a bestseller. ‘I thought I’d never be able to write a book,’ says Jo. ‘I’d always struggled with spelling and grammar. But I tried, and found I loved it. Now I don’t struggle with writing at all – I struggle when I stop writing. When I finished my first book I had tinnitus for weeks afterwards. Handing over the manuscript was like giving my baby away. I felt so flat afterwards.’

Now she’s produced her second book, Home Baking, featuring mouth-watering biscuits, cakes, breads and also a selection of simple supper dishes to bake in the oven. The delicious honey madeleines and the Eccles cakes are here, along with tempting dishes from stem ginger cheesecake to samphire, pea and mint quiche. Her piece de resistance is a toffee apple croquembouche – a tower of choux buns with a toffee-apple filling finished with wisps of spun sugar.

‘I loved the idea of fairground treats made into something really elegant and beautiful,’ she says. ‘But there’s something here for everyone. My apple turnovers can be made in 30 minutes, from cupboard to table.’

So why does she think The Great British Bake Off has been so successful? ‘Because it’s gentle, it’s not massively competitive and the recipes in it are obtainable,’ she replies. ‘That’s what I wanted my cookbooks to be like too. I hate opening a cookery book where the ingredients are pages long and you have to source them from Outer Mongolia.’

Recent food scares have also prompted concern over the sourcing of ingredients. ‘I know exactly what you’re eating there,’ she says, as I munch my way through her Eccles cake. ‘There are no hidden additives or E numbers. I don’t want something that’s going to last for weeks in my cupboard. I want something that’s fresh and delicious and is going to go off, because it’s not full of preservatives.’

Jo is keen to write more books and develop her cookery school. But most of all, she would love her own TV show. And while she can’t confirm anything, I sense that could soon be on the cards. It’s inspiring to see how Jo has transformed her life so completely.

‘I think it’s fate,’ she says. ‘If my friend hadn’t called me that evening, when I was sitting there with the laptop, I may never have applied. You never know what’s just around the corner. Your life may not be going the way you want it to, and within seconds, things can totally change.’