We bought a flat and made an incredible discovery... there was no trace of it on any of the paperwork

A couple were stunned when they discovered a mystery room while renovating their new home. 

British TikToker Erin Cloudy was renovating her house when she made a shocking discovery - a hidden door under the stairs that led to a whole secret room 'as big as her flat,' and a network of underground tunnels.

She shared a video on TikTok and took viewers along as she explored her bizarre new property.

Posting under her handle @erincloudy, she shared the moment they stumbled across the hidden door.

They had just started knocking down a wall under the stairs - not expecting to be met with another staircase leading down to an old door.

British TikToker Erin Cloudy was beginning the renovation process on her new home when she made a shocking discovery - a hidden door under the stairs that led to a whole secret room 'as big as her flat,' and a network of underground tunnels

Posting under her handle @erincloudy, she shared the moment that she and the people working on the renovation with her stumbled across the hidden door

Filming the incredible discovery, Erin said: 'Under the stairs, we knocked it through, and you look through this hole and it's just a f****** staircase. What the f***? and a door?

Someone who was helping her out with the renovation noticed: 'It goes down even further' with yet another staircase behind the door, leading down into darkness.

Unable to conceal their shock, they made their way through the door and exclaimed: 'It's as big as your flat down here. Oh my God'.

The video cut off just before they got to the secret room, but Erin quickly filmed a second part to keep viewers updated. 

She wrote in the caption: 'So my flat is "basement flat" there has been no mention of anything underneath me, verbally or on the deeds. We were curious about storage under the stairs and decided to take a look'.

Following the hidden tunnel, they found themselves in a huge underground room, complete with an old fireplace and a functioning light.

Erin's flat is on the bottom floor, with three other flats above her and no mention of anything below her. 

However, the surprise didn't end there, as she found a network of underground tunnels leading off from the secret basement room, some of which had access to the streets above.

Following the hidden tunnel, they found themselves in a huge underground room, complete with an old fireplace and a functioning light

However, the surprise didn't end there, as she found a network of underground tunnels leading off from the secret basement room, some of which had access to the streets above

Equipped with her phone camera and a torch, she began to explore the whole new level she didn't know she was getting.

The TikToker penned: 'I cannot cope with this building! I wasn't freaked out before but I am now! As you can see there are a couple of rooms I'd have to crawl into and I'm not sure I'm, willing to! 

'I wanna know what the purpose of them was and why they don't have full sized doors?! Any ideas?'

Making her way through the dingy crawlspace, she said: 'It's like Barbarian, oh it stinks. 

'Oh my days, it keeps going. Oh I don't know, I can't go in there. It keeps going. I really am blessing this house.'

She panned the camera to what seems like a never-ending passage that leads off to smaller spaces.

Now fearful of what began as a fun discovery, she added: 'It goes up to the road. This is all underneath me. I'm not going to be able to sleep'. 

Social media users couldn't believe what they were seeing and urged the new homeowner to show them more.

In one clip, Erin showed viewers what her whole building looks like from the outside, explaining how she had no idea about the basement floor.

She said:  'Okay so, this is the entire building and there are three flats above me, and this is my level and my door. 

'Then, there's a little courtyard and there's this, which I did notice when I bought the flat, but I just thought was a little coal house.

'Then when I look closer there's a window, which I think is the window in the secret room. We're gonna clear this out and get in there.

'Also, when I viewed the house before I bought it, this little top of the window had loads of plant pots there so I didn't actually see that bit.'

She panned the camera to what seems like a never-ending passage that leads off to smaller spaces

In one clip, Erin showed viewers what her whole building looks like from the outside, explaining how she had no idea about the basement floor

The video series, which was originally posted back in January, has caught the attention of millions of users, who flocked to the comments to give their verdict on the unique flat

As well as the tunnels, the property has some interesting quirks that left Erin with an abundance of questions.

In the tunnels and the small courtyard area at the front of the building, she found some barred-up windows and doors that had nothing behind them but bricks.

She questioned: 'There's another barred up window. Where does that go to? It's a wall I think, someone's bricked in a window.

'That's the basement. For some reason it's got these bars that have been bent down.'

On her level of the building, she found a square shaped hole in the wall, which she believes could have been a proving oven.

She guessed: 'Maybe this was the kitchen quarters and the lower basement was the servant quarters.'

The video series, which was originally posted back in January, has caught the attention of millions of users, who flocked to the comments to give their verdict on the unique flat. 

One user questioned: 'Has nobody seen Barbarian?,' with a second adding: 'Absolutely not. I've seen Barbarian. I'd seal it up and move out'.

The 2022 horror film which viewers keep comparing the flat to, sees a young woman discover the rental house she booked is already occupied by a stranger and has some very dark secrets within its underground tunnels.

A third penned: 'People don’t understand how much of a bonus this is, a little bit of renovations, and you’ve practically doubled your floorspace'.

'That's a really neat room, but why was it closed off?' asked another commenter.

Meanwhile, someone else sneakily advised: 'Don't say anything, just move in. Storage'.

'You have to look up the history of the property and see if you can find the reason they boarded it up,' suggested another.

Most viewers, however, were terrified of the discovery, joking to keep them updated with any 'paranormal activity' and that the bars were broken due to a 'demon'.

Someone quipped: 'If something is sealed by cement and wood and you keep going and it's sealed again, it may need to stay sealed.'

Another wrote: 'With each video, I'm expecting you to turn the corner and there's a skeleton laying there'.

Erin hasn't updated her followers on the home since the end of January, with many begging for more videos.

MailOnline has contacted the TikToker for comment.