Image copyright PA

A difficult and disgusting operation to clear London's largest "fatberg" from a London sewer raises a number of issues about our approach to waste disposal.

Fatbergs are not natural - they are creatures of the modern age - and the blockages they cause can lead to raw sewage flowing up into shops, offices and people's homes.

It is not a subject for the faint-hearted but there are 10 large fatbergs in London right now and hundreds of smaller ones across the country.

They form when oil and grease, poured down drains, coagulates around the likes of tampons, baby wipes and condoms flushed down toilets.

The result is the creation of a pale, tough substance with the strength of rock - a form of artificial geology that in the case of the Whitechapel fatberg has choked 80% of the flow of the sewer.

The basic problem is that we inherited a network of underground sewers built 150 years ago that was never designed to cope with what's now thrown into it.

However far-sighted Sir Joseph Bazalgette and his fellow Victorian engineers were, they can have had no idea how the populations of our cities would explode and how changes in diet and lifestyles would create a potentially devastating onslaught.

The gentle gradients of their designs were meant to create steady streams of human waste and water - not exactly fragrant but "they don't smell bad if they're working properly," one sewage expert told me.

Image caption The smell from the Whitechapel "fatberg" was bad enough to cause David Shukman to gag

By contrast, the noxious blast of fetid air that rose when the manhole cover was lifted during yesterday's operation was enough to make me gag and cover my face with my jacket.

Three metres beneath the heavy East End traffic, a monstrous mass of fat is acting in the same way that plaque does in arteries and, as with heart trouble, the problem is usually unseen until it's too late.

As the engineers donned what looked like spacesuits to head underground - double gloves, hoses bringing fresh air, electronic sensors to spot dangerous gases - a small crowd gathered to watch.

The street is lined with fast-food restaurants, just the kind of places that have flourished as the demand for fried takeaways has soared. One of the onlookers wore the striped apron of a chef.

Research by Thames Water mapped the locations of fatbergs and of restaurants, and came up with a remarkable conclusion: if you live within 50 metres of a fast-food place, your chances of being flooded with sewage are eight times higher than if you live further away.

So the company has sent teams to visit more than 700 restaurants to explore what steps they're taking to stop the flow of fat leaving their kitchens.

The answer? The vast majority are doing nothing at all.

Thames Water executives believe this is not through wilfulness but ignorance. There are devices to trap fat, and they cost only a few hundred pounds, but few seem to have heard of them.

So the first step in the battle against the bergs is to encourage, cajole or shame restaurant owners into forking out for the small boxes that sit atop a drain and clean the flow.

Talks with the big chains are under way. The response so far has been one of surprise that the scale of the problem had not been realised, so maybe the coming months will see fat traps becoming more common.

Image copyright Getty Images Image caption Fatbergs have to be cleared out of narrow tunnels, often by hand

But the survey also found that where a small number of restaurants had invested in the devices, few had maintained them. So there lies another challenge.

And the key to all this may be our own attitudes - whether any of us demand change.

Just as it's become more common for people to expect vegetarian options or food prepared without gluten or dairy products, might anyone demand to know whether a restaurant's kitchen is sewer-friendly before paying for a meal?

There's now a term for our unthinking but damaging approach to what we flush away: sewer abuse.

One answer is to support and expand schemes to collect restaurant fat and turn it into fuel - a logical form of renewable energy - and this is what will happen to the fatbergs.

At the heart of this question is our consumer culture's approach to waste, the belief that we can just chuck anything away without consequence, "away" being an abstract and distant concept that we need not care about.

But "away" is a real place, like an east London sewer jammed with a fatberg weighing the same as 11 buses, and now being chipped away by shovel by brave teams straining in heat so intense they can last only 40 minutes at a time.

The image of a dark figure hunched in a tiny tunnel working by hand is startling to us in 21st Century Britain. But in a curious way, it's also an unintended throwback to the grimmer Victorian times when the sewers were built in the first place.