The loan will support the six-strong group’s expansion for the next three years, with at least three further restaurants set to open in 2019.
Flat Iron, which was founded by Charlie Carroll as a pop-up above a London pub in 2012, will launch a restaurant in London Bridge on 21 January, followed by a site in Spitalfields this summer and ‘at least’ one additional opening this year.
It comes after the steak group received a £10m investment from private equity group Piper towards its expansion in 2017.
“We are optimistic for the future, trading remains strong and we are seeing an increasing number of quality opportunities on the property side,” says Carroll.
“We are looking forward to the chance to acquire some really amazing sites and are appreciative that ThinCats were able to see past the wider industry headlines and provide us the financial means to support our growth.”
Flat Iron's £10 steak deal and broad no-reservations policy has seen it create considerable peak-time queues in London, but the brand has yet to venture outside the capital.
Speaking at the Casual Dining Show in 2018, Flat Iron's managing director Jo Fleet said there were ‘no immediate plans’ to open beyond London due to the uncertain economic climate and the difficulty of maintaining company culture across a broader number of sites.
Thincats has previously backed restaurant groups Abokado and Koh Thai Tapas.