A woman claims she went to look at a room, available to rent at a reasonable (for London) £500 a month, and found out all that was being offered was a Harry Potter-style bed under the stairs.
Alex Lomax, 23, tweeted the picture she claimed showed the "room" she went to look at in Clapham, south London, complete with boxes of Daz and other people's coats, but without any actual 'room'.
She claimed the landlord was "absolutely serious" about the offer and she surreptitiously took photos while he was away making himself a coffee.
The setup is reminiscent of how boy wizard Harry Potter is made to sleep by his cruel aunt and uncle the Dursleys in JK Rowling's books.
She told ITV News: "I didn't even stay long enough to check if there was a mattress, and the landlord seemed absolutely serious.
"I asked him if he was joking and he seemed shocked I'd even asked. I took the pics secretly when he was making himself a cup of coffee, the cupboard was right next to the kitchen.
"I expected a normal single room, definitely not this. I left as quickly as I could."
She claimed the bed was advertised on website London2Let as a single furnished room.
The advert Ms Lomax linked to on Twitter says: "We are looking for a friendly, open-minded and outgoing person to join our house share in a great period house in Clapham.
"We’re a good bunch and like to chill out a lot together – not really looking for somebody that just wants to stay in their room. Room comes with a bed. Bills to be shared – approx. £60 per month each. Easy access to local tube stations."
The Huffington Post UK has tried to contact the landlord but had not received a response as this article went live.
Roger Harding, director of communications, policy and campaigns at housing charity Shelter, said the cost of living under the stairs was "clear proof that the capital’s housing market is completely broken".
“Even the Dursley’s didn’t charge £500 a month," he said. “Sadly, it’s ordinary Londoners who are suffering at the hands of our housing crisis, with many young people and families barely able to pay the rent, let alone save for a home of their own."
He added: “This problem won’t go away by waving a magic wand, so the Mayor has to get serious about building the genuinely affordable homes that we desperately need. Otherwise we run the risk of seeing huge swathes of London becoming the preserve of only the well-off.”