From Pop-Up to Permanent: Five Popular London Restaurants That Are Here to Stay Bonnie Gull Seaside Shack Here today, gone tomorrow? Not any more, as five of London's most popular pop-up restaurants settle down with brick and mortar spaces of their very own. Pop-ups have long been a fixture on the London foodie scene, attracting the U.K. capital's trendiest gastronomes with one-off menus in temporary and often unusual locations. Now many of them are landing permanent homes. As a business strategy, it makes sense: restaurateurs can experiment, make mistakes and build a customer base all before sinking a lump sum into a long-term lease. From a steak joint that only serves one cut, to a nostalgic seafood shack in Central London, these five pop-ups are here to stay. Will they retain the improvisational spirit and the novelty that won them a following in the first place? That's for the city's fickle diners to decide. LIST: 10 Things to Do in London Flat Iron The only item on the menu at Flat Iron is the eponymous cut of steak, second in tenderness only to the filet mignon. Butchers seeking it must first strip the muscle of its sinew, then devein the hunks to find their marbled treasure. Each slab, together with sides and sauces, goes for about $17 at Flat Iron, a summer pop-up now permanently housed in a stripped back old Soho building, complete with long wooden tables and vintage overhead lamps. A basement bar serves up mean cocktails as well as an off-menu dessert of fresh donuts. Back in 5 Minutes Swedish head chef Frederick Bolin smokes his own ham hocks and bakes his own bread for this once roaming supper-club that's now rooted in a clubby, 30-seat space behind a clothes shop on Brick Lane. The menu is friendly, elegant European fare - think white bean soup, duck confit and eton mess. Look out for the Scandinavian-themed evening on the third Saturday of each month, and the Wednesday night "dinner club," when a three-course meal is enjoyed communally. Bonnie Gull Seafood Shack If you like tactile dining, try Bonnie Gull, which served one of the largest Devon king crabs we've ever cracked meat out of. This is a diner you'd expect by the seaside, festooned with nautical whimsy and offering an unpretentious menu of fresh seafood to be coaxed off shell and bone. The fish is U.K.-sourced, with each day's catch pinpointed on a chalkboard map. Oysters are a mainstay at the raw bar, along with sharp, creative cocktails, often accompanied by a shellfish garnish. This permanent space in Central London is the net result of not one but three pop-up incarnations - and it's lost none of its heart in the process. MORE: London's Hottest Chefs" Collective Upstairs at the 10 Bells A pair of young chefs started Ten Bells as a pop-up restaurant serving Michelin-star-worthy food at downhome prices. Since going permanent in June, that hasn't changed, with locally sourced, occasionally unorthodox ingredients prepared as inventively as you might expect from a duo that both did time at the current World's Best Restaurant, Noma. A typical menu might includes starters of treacle-cured salmon and chestnut and truffle soup, before moving onto amain course of hake, caulifower and brown shrimp, and ending on apple fritters and sour cream. Beard to Tail James Lowe and Isaac McHale have also gone on to stage pop-up dinners in Europe and the U.S., while their newest private supper-club, the Clove Club, has proved so successful it will also be putting down permanent roots next year, in Shoreditch Town Hall. Pop-ups often make a statement about food and how it should be eaten. Beard to Tail originally sprung to life as an evangelist for animal flesh in all its forms. Trotters, cheeks, liver: if it was once part of cow or pig, Beard to Tail would serve it. The permanentrestaurant opened this September in the heart of hipster Shoreditch, serving the same visceral menu with nary a hint of vegetable and some seriously stiff cocktails. Don't bring salad-eaters - the only salad on offer is made with offal.