The chef will begin serving his full menu above the pub next week.
Yesterday Borthwick took to social media to announce his departure from Merchants Tavern, which he opened with his partner Angela Hartnett and Canteen owners Dominic Lake and Patrick Clayton-Malone in 2013.
He tweeted: “It’s all change…I stepped down as head chef @merchantstavern earlier this year, and I want to say a big thanks to all the team for their hard work and dedication over the last 5 years, it’s been a blast and I know you will go on to great things. Go for it!”
He added in a later post: “So from next week I will be cooking @frenchhousesoho. I’m doing what I love best!”
Merchants Tavern sous chef Pippa MacDonald has now been promoted to the role of head chef following Borthwick's departure.
She has cooked at Scott's in Mayfair, J Sheekey and Tom Aikens' Hong Kong restaurant The Pawn in Wan Chai.
Like Hartnett, Borthwick previously worked for Gordon Ramsay, starting at his Amaryllis restaurant in Glasgow before moving on to The Connaught.