The 212-cover site, set to open in November, will feature a 68-cover central bar, a large open kitchen and a mixture of stand-alone seating and leather booths.
It will replace Thyme Kings Cross, also owned by Whitbread.
David Murdin, chief operating officer of brand developments at Whitbread, said: “We’re very excited to be launching our flagship site in London following its success in Birmingham."
He added: “We’re keen to develop the brand further and aim to have several venues open by the end of this financial year.”
Bar + Block serves an all-day dining menu focusing on hand-cut steaks as well as a range of breakfast, lunch and dinner options and specials on rotation.
Dishes on offer at the Birmingham site include garlic king prawns cooked in white wine with lemon juice and ciabatta; slow-cooked pork belly with wholegrain mustard mash, apple and watercress; and triple chocolate brownie with chocolate toffee sauce and vanilla ice cream.
The food offer at the London site will be accompanied by a range of craft beers and ciders, many by BrewDog, as well as cocktails and an extensive wine list.
Bar + Block had been designed specifically to function on the high street, Murdin previously told The Morning Advertiser, in contrast to Beefeater sites, which were primarily in rural locations.