By Martin Stew: ITV London Presenter
Under this central London manhole is a sewer in one of the worst states Thames Water has ever seen.
Why I agreed to go down there I'm not sure. The smell coming off the guys who were down there wasn't great.
What I found at the bottom of the ladder 10 metres below Whitehall is even worse than feared.
A fatberg is when people put fat and oil down the sink. It all congeals into these big huge rocks like this that block up all the sewage system. It's like concrete.
Much like a clogged artery, the fat and rubbish reduces the flow which can pass through the sewer.
To remove it requires hug machines to suck the muck.
It costs about £12 million a year - a million pounds a month it's costing us as a business. We pay for it but the customers pay for it too. They pay for it through their bills they also pay for it through their bills and also the misery because its not nice if you get internal flooding.
So after my trip to the sewer, I have the message 'bin it don't block it' ringing in my ears and a foul stench burning my nostrils.