A Mail on Sunday investigation today exposes how Google has cashed in on a sickening YouTube video that shows viewers how to kill someone in a stab vest like the one worn by PC Keith Palmer when he was murdered in the Westminster terror attack.

The vile video was online for six months before the outrage and could be viewed for days afterwards, despite widespread warnings that UK jihadis use such material for training.

The seven-minute film, entitled How To Pierce A Stab Proof Vest, demonstrates how to plunge a knife through protective body armour and has been viewed nearly a quarter of a million times – generating thousands of pounds in advertising revenue.

The video was made by German weapons obsessive Jörg Sprave, who proudly displays on the wall of his living room a framed award from YouTube for attracting a million subscribers to his films.

German weapons obsessive Jörg Sprave, pictured, uploaded a video to YouTube showing how to kill someone wearing a stab vest

The sickening footage, pictured, showed him demonstrating how and where to use a knife on someone wearing body armour

The Mail on Sunday easily found the film online despite promises made last week by YouTube owners Google to crack down on extremist material.

Last night, Home Secretary Amber Rudd condemned the video and demanded that YouTube take action to ensure similar films are banned.

She said: ‘We will not tolerate the internet being used to hide terrorist activities or, as The Mail on Sunday has revealed, provide information to assist them in their terrible activities.

'Following my meeting last week, major internet companies including Google have agreed to work together in an international forum to ensure this sort of material isn’t available. I will want to see early and effective progress.’

And Labour’s Yvette Cooper, chairman of the Home Affairs Select Committee, said: ‘The idea that YouTube and Google should profit from something so depraved is appalling.

'When are Google going to get their act together and stop making money out of vile hatred?’

The revelation comes little more than a week after Khalid Masood mounted the pavement on Westminster Bridge in a hired car, killing three people, before killing PC Palmer by stabbing him through the chest.

Yesterday, after being contacted by The Mail on Sunday, YouTube removed the video but it had already been online for more than six months, earning thousands of pounds in advertising revenue from companies including Netflix – though they cannot choose the YouTube videos in which their adverts appear.

Sprave was even given an award by YouTube for attracting 1,000,000 subscribers to his channel, despite widespread warnings that UK jihadis use such material for training

In the film, Sprave stands in a wooded area of his back garden in southern Germany explaining to viewers how they can modify a knife and its handle so it can be used to pierce a protective vest.

The one he uses is similar to the vests worn by Metropolitan Police officers.

He thrusts the knife through the stab vest which is attached to a makeshift dummy. ‘Wow, look at that, I pierced the safety vest,’ he boasts, adding: ‘As you can see, it definitely pierced deep enough to cause major harm.’

One member of the public commenting on the video wrote: ‘Thanks to you, a lot of people now know how to kill a police officer.’

When another YouTube viewer questioned why Sprave would teach people how to pierce a stab vest, he replied chillingly: ‘Because I can, obviously.’

And another outraged viewer wrote: ‘I work in corrections [prisons]. You are putting my life in danger.’

Sprave, 51, started making films on YouTube as a hobby around eight years ago. He became so successful with his channel that in January he gave up his job with a German electronics firm.

Yesterday, when approached by The Mail on Sunday, Sprave, who has 120,000 subscribers in the UK, defended the video.

Interviewed at his former hunting lodge home in the village of Rothenburg near Heidelberg, he said: ‘I just want to show that people who wear these vests should not feel invincible.

‘They are still vulnerable. These vests should not be described as stab proof.’

Wearing a black T-shirt emblazoned with the slogan Fight Fire With Fire, he added: ‘I just test things and make videos to review all kinds of things like cameras, knives and air guns.

'If they change police equipment because I have shown it is vulnerable then I may be saving some lives.

‘I feel sorry about what happened to the policeman in London. He should have had a gun to protect himself.’

Police in the German state of Hessen were unavailable to comment yesterday. An unofficial police source in the local town of Erbach said: ‘We had to check on him once, but we found nothing wrong.’

Sprave’s other videos include an 11-minute clip entitled: ‘Shooting right through police riot gear?’ which has been viewed more than half a million times.

The video has been taken down days after terrorist Khalid Masood, left, fatally stabbed PC Keith Palmer, pictured right with a member of the public, in Westminster, and it the stab vest it showed was similar to one worn by the Met Police officer on the day of his death

During this video – which YouTube has also now removed – Sprave uses a custom-made weapon to fire a steel-tipped arrow through a German police riot shield.

‘Well, I think that policeman is dead,’ he says, inspecting the damage.

Internet users clicking on the stab video last week saw adverts automatically play on different occasions for Netflix, internet security firm OwlDetect and property website eMoov.

An advert for Finnish music festival Flow Festival 2017 played before the riot shield video.

Those who post videos typically receive up to $7.60 (£6.08) per 1,000 views of an advert, meaning Sprave would have made nearly £1,500 from the stab video and over £3,000 from the riot shield video.

YouTube would have earned approximately £1,200 for the stab video and about £2,500 for the riot shield video.

Calum Macleod, vice-chairman of the Police Federation of England and Wales, said: ‘That anyone thinks it is acceptable to share content that could further put police officers, or any emergency service workers, in harm is deplorable, disappointing and upsetting.’

Yesterday, YouTube said it had permanently removed both videos but refused to reveal how much money it had made from them.

A spokeswoman said: ‘We have clear policies against inciting violence and harmful or dangerous activities and remove content that breaks our guidelines when we’re made aware of it.’

HOW KNIFE 'EXPERT' WAS HONOURED BY WEB GIANT Sprave makes money by posting his horrific videos on YouTube. Adverts, from companies including Netflix, left, automatically show when the videos are watched and Sprave makes money from each 1,000 views. YouTube, owned by Google, also takes a cut from the advertisers. Sprave made thousands from the video of the stab vest attack, seen by a quarter of a million viewers, and another clip showing how to pierce a police riot shield, seen by half a million viewers. Videos are his main source of income and he’s won an award from YouTube, right, for attracting a million subscribers to his channel, called Slingshot. Sprave makes money by posting his horrific videos on YouTube thanks to adverts from companies including Netflix, pictured Advertisement

A spokesman for OwlDetect said: ‘We were not aware that our product was being advertised before this video.

‘We have stopped this advertising immediately and will review the ways in which we advertise with Google and YouTube.’

Russell Quirk, founder and CEO of eMoov, said: ‘We and other advertisers have no control over which content these [adverts] are associated with.

'We have contacted Google and have demanded our adverts are removed immediately.’

A Flow Festival spokeswoman said: ‘We will contact Google and ask them to blacklist this video on our campaign so that Flow Festival video ads cannot be displayed in connection to the videos by this specific YouTube user account.’

A Netflix spokesman said: ‘We employ numerous filters to avoid having our content appear on sites or videos that clearly don’t represent us or our values.

‘While that works well most of the time, there are a small number of instances where it doesn’t and we are working closely with Google to close that gap further.’