She is the youngest of three children, of her father William, a farmer, and mother Doreen, who worked as a waitress at a local restaurant.

[11] At the age of fifteen, Smyth held a job over a holiday period at a local restaurant, inspiring her to become a chef.

She left school at sixteen to study catering at Highbury College in Portsmouth, Hampshire.

[13] She left that post to work full-time at Terence Conran's restaurant at Michelin House, London.

She followed this with a six-month period in Australia working for a catering company,[11] and on her return to the UK she staged at a variety of restaurants including The Waterside Inn and Gidleigh Park.

[1] Smyth was appointed Member of the Order of the British Empire (MBE) in the 2013 Birthday Honours for services to the hospitality industry.

[16][17] Smyth was awarded a perfect ten score by the Good Food Guide of the UK's 2015.

[24] Oncore, on the 26th floor of the Crown Sydney in Barangaroo opened in November 2021 with head chef Alan Stuart.