The house is wedged between a doctor's surgery and a hairdressing salon, and only identified by a streak of dark blue paint.
The five-floor house in Shepherd's Bush is just 1.6 metres at its narrowest point and is on the market for £950,000 ($1.3 million).
The unusual property was originally a Victorian hat shop with storage for merchandise and living quarters on its upper floors.
It was built sometime in the late 19th or early 20th century.
In a nod to its past, the house still has an old-fashioned glass shopfront with a lamp in the shape of a bowler hat.
David Myers, an assistant sales manager at Winkworth estate agents, which is selling the property, said the house was worth its price tag because it was "a unique part of London history".
"It's a bit of London magic," Mr Myers told AFP.
The dimensions of the house differ throughout.
While the kitchen at the end of the lower ground floor is the house's narrowest spot, it opens up into a dining area that is nearly double the size.
A five metre-wide garden lies beyond behind French windows.
The ground floor, which now contains a reception where the old shop would have been, and the first floor are of similar sizes.
The first, with a bedroom and study, also has a roof terrace with commanding views over the chimney pots of West London.
Spiral stairs lead from the second floor to the bathroom and shower room, and up to the master bedroom on the third.
It is accessed by a hatch that opens through the floor to save on space, and the built-in bed takes up an entire end of the room, fitted into the walls on either side.
Mr Myers said the house was for a "young couple or an individual" who saw "the beauty for what it is".
He said "unique" period features mixed with art deco and other eclectic interior designs made the house appealing to buyers who were "arty" or "bohemian".
"There are houses in London that are five storeys but don't have such a unique space, such individuality," Mr Myers said.
He said past owners had "all put their own stamp on it".
The price of the house is prohibitive for most in Britain, where the average house price is £256,000, but typical of London's property market.
"It's more expensive because we have everything going on," Mr Myers said.
"From somewhere like Shepherd's Bush we can be in the very heart of London in within 10 to 15 minutes."
If it meets its asking price, the house will have doubled in value since 2006 when it was sold for £488,500, the UK's land registry says.
By Mr Myers's estimations, the house is worth more because of its dimensions.
"In a lot of parts of London people will use the pound-per-square-footage mark and use it as a benchmark for what properties are going to be worth," he said.
"It doesn't always work like that. When you've got something as individual as this, the price has to be reflected in that."
The impact of the Covid-19 pandemic, which Mr Myers said had drawn families away from London to take advantage of the space afforded by lower property prices outside, meant the house was unlikely to sell right away.
"In a situation such as Covid, where all the fish in the sea have thinned out quite considerably, there's not so many buyers out there," he said.
"And there are less buyers for a unique, individual property such as this."
But ultimately he was undeterred.
"It's chic, it's beautiful, and that's why this house will sell," Mr Myers said.
