A shocking video shows a bucket full of black sludge extracted from just four seats on the London Underground by a cleaner.
He posted the footage as a publicity stunt for his company, but viewers were left horrified by the grimy truth of Tube seats.
Steven James - also known as Mr Carpet Clean - filmed himself power-washing the seats on a Northern Line train at Camden Town station.
He then goes in with an electronic carpet cleaner to get out the more deeply embedded dirt.
But the real shock comes when he shows the yellow bucket filled with murky water and grime.
A bucket full of black sludge extracted from just four seats on the London Underground
He filmed himself power-washing the seats on a Northern Line train at Camden Town station
Steven James - also known as Mr Carpet Clean - said I wont be doing that again
He is heard saying: Health warning. Where do you go after travelling on the Underground?
Disgusted viewers replied, calling the seats absolutely filthy and saying that is the reason they take off their outside clothes as soon as they get home.
One comment said they always stand because theyre afraid of how dirty the seats could be.
Speaking to the BBC, Mr James said that seeing the resulting sludge was the pinnacle of the therapeutic side of cleaning.
But Transport for London claimed he was putting other passengers at risk by emptying a bucket of water near a live rail.
He then goes in with an electronic carpet cleaner to get out the more deeply embedded dirt
The footage was posted as a publicity stunt for his company, but viewers were left horrified by the grimy truth of Tube seats
Mr James said I definitely didnt put anyone at risk but warned viewers that they shouldnt attempt to clean the seats themselves.
I wont be doing that again, he added.
TfL said its cleaning schedule for Tube trains consists of two different levels of cleaning.
It has daily pre-service cleans and a deep clean every 28 days.
MailOnline contacted TfL for comment.