Clare Smyth is the chef behind Core, one of Britain's most successful restaurant openings. She was the first woman to helm a three Michelin star restaurant in the UK. In 2018, she was awarded the World's Best Female Chef and she catered Prince Harry and Meghan Markle's wedding (she's sworn to secrecy on the details, although she says, despite reports to the contrary, that it "definitely was not posh burgers, pork belly and candy floss"). She's a regular guest judge on Netflix's cooking show The Final Table and she's in the country now for Channel Ten's MasterChef Australia. But back when Clare Smyth first started at London's Restaurant Gordon Ramsay as a junior chef in 2002, she was told she wouldn't last a week.

Ramsay and the rest of the kitchen team should have known better. The early-20-something girl from Northern Ireland had already shown signs of her steely determination, leaving home at 16 against her parents' wishes to pursue her dreams of becoming a chef.

The absence of a dining scene in her home country meant Smyth looked for opportunity in England, securing herself an apprenticeship (with board) at Grayshott Hall, a health spa in Surrey, and enrolling in a college course outside Portsmouth. After gaining her NVQs (national vocational qualifications), Smyth landed a job as an 18-year-old commis chef at London's Bibendum, where she worked for a year before leaving for a sous chef role at St Enodoc Hotel in Cornwall. Aside from a series of stages with chefs like Heston Blumenthal and the Roux brothers that Smyth worked during holidays and between jobs, the next kitchen she saw the inside of was Ramsay's.

"It was tough, but I loved it and I thrived on it," she says. "The food was the best in the country and Gordon was on such a trajectory then, so to be a part of that was phenomenal. I grew up in that environment and I learnt so much."

But like many women keen to get ahead, Smyth had to work twice as hard as everyone else. Even after she'd left to work with Alain Ducasse at his Louis XV restaurant in Monte Carlo and then returned to Restaurant Gordon Ramsay to take up the head chef role, she was putting in 19-hour days. "I didn't take a holiday for the first two years, I was so determined to prove myself," she says.

Smyth calls this the toughest point in her career. "It was a difficult time for the group, and I was very young," she says. "I didn't know if I could do it. It was my first head chef role and so I didn't have anything to measure myself by. I said to Gordon, 'I don't know if I'm good enough because I haven't won the three stars. I just have to step in and start delivering three star dishes'. He just said, 'Don't be stupid'."

I'm not cooking for Michelin stars.

At just 28 years old, Smyth became the first woman to take up the head chef role at Restaurant Gordon Ramsay and the first woman to helm a three Michelin-starred restaurant in the UK, ever. She would stay with Ramsay for 10 years, maintaining his three Michelin stars and "maximising every guide in Britain" for the duration. By the time she left, "I had done my job," she says. "I left it at a high point. I walked out the door and I dropped the mic."

In August 2017, Smyth made history when she opened her debut restaurant, Core, in London's Notting Hill, to two Michelin stars, 10/10 in the Good Food Guide and five AA rosettes – an unprecedented result for a restaurant in Britain. Even so, "It isn't what I want it to be, yet," she says. "I mean, we're on the right path, but I still feel like we haven't scratched the surface. There's a lot more in the toolbox and right now we're just evolving it."

For those wondering, the kitchen Smyth runs is very different to the one her mentor ran, not least because of the short work week (just eight services per week) she enforces. But, she admits it took her a while to get to that stage. "I thought I had to shout and swear to prove myself, but as I grew more confident in myself and who I was as a person … my kitchen now is incredibly quiet," she says. "People would say I'm the opposite of Gordon," although she's quick to add that most of what people know of him is based on his television persona. She also concedes that there's a "calm steeliness" to her approach that can unnerve others.

The name Core refers to the heart or the seed of something new, which is exactly what it is for Smyth. For the first time in her career, she's been able to move away from the shackles of the high-end, classically French style of cooking in which she was trained and focus instead on the food and culture of her adoptive Britain. Her restaurant uses British produce, all the cutlery and crockery is made in Britain, and signature dishes like her Potato and Roe (a potato served with beurre blanc, herring and trout roe) and her Lamb Carrot (made from whole carrots, including the tops, and lamb neck) highlight British ingredients. "We take the piss out of our own culture, a bit," she says. "I call it informal fine dining, but it's informal luxury, so it's the best of everything, but we don't have any of the formality with it. There's no dress code, I play my own playlist and we have fun."

Her early success with Core means eyes are on her for the 2020 Michelin Guide awards, but after maintaining them for so long for Ramsay, is she concerned with earning three stars of her own? "I'm not cooking for Michelin stars," she says. "What I'm more worried about is the joyability factor – that, to me, is way more important than anything else. It's people walking out the door thinking, 'I really enjoyed myself'.

"The fact that our success happened so quickly is something I don't take for granted – I'm incredibly grateful for it. I'm grateful that people want to come and eat there, and it's our job to work hard and make sure that we make people happy and want to come back. That's what's important."

Quick-fire corner

Your go-to midnight snack?

I would say my guilty snack is salt and vinegar crisps.

Your favourite kitchen weapon?

It's got to be a temperature probe - a spike where you can check if things are cooked or not. That's the thing I use the most.

Your non-cooking ninja skill?

I would have been a professional horse show jumper if I wasn't a chef.

MasterChef Australia's Legends Week featuring Clare Smyth starts Sunday, May 19 at 7.30pm on 10.