David Wilson was on the police's radar two years before the National Crime Agency came knocking on his door.

And on Wednesday, the 36-year-old, of Kirstead, King's Lynn was jailed for 25 years after previously admitting 96 child sex crimes against 51 victims at a hearing in November.

Norfolk officers had become aware of his online activities and raided his house near the Queen Elizabeth Hospital in April, 2015.

But Wilson was working away in Nottingham when they broke his door down. When police caught up with him, he claimed he had mislaid his phone on the way home.

Without the phone, there was not yet enough evidence to put before the courts.

Wilson was the coach of a youth football team. He was suspended after police informed the Norfolk FA that he was under investigation, as enquiries into his activities continued.

Eastern Daily Press: David Wilson's demands on his victims became more obscene, as he carried on offending despite being arrestedDavid Wilson's demands on his victims became more obscene, as he carried on offending despite being arrested (Image: NCA)

Despite being arrested and interviewed, Wilson carried on offending. His crimes became more extreme, making increasingly obscene demands on his victims, as the months went on.

"I really think he couldn't help himself," said one officer involved in the investigation. "It was like some sort of mental illness.

"It developed over time and he became progressively worse, which is not an unusual characteristic of an offender. What will happen is they need to move on and do other things to gain the same stimulus, a bit like drugs. He became more and more dangerous in terms of his offending."

Wilson, who lived with his mother on Kirstead, was in denial about his crimes even as the net was closing in around him.

"In terms of his persona, he was a pretty nondescript bloke," said the retired detective. "Not the sort of person you'd see walking down the street and think he's a really, really bad man, like a paedophile.

"I've dealt with numerous criminals of all ages, from all backgrounds, from all walks of life. There are some you can deal with, there are some you just don't like and he fell into the latter bracket without a doubt."

While Wilson had around 40 known victims from Norfolk. But police fear many more may have been so ashamed of what Wilson made them do they have not come forward.

"They're the hidden figures," said the former officer. "You'll have a massive pool of people who've been affected by this guy, a lot of victims will go unheard and carry it with them.

"There were kids who had interactions with him who were so ashamed, mortified, embarrassed - they thought they'd be in trouble."

Many did not even tell their parents what had happened. The first some victim's families knew was when police arrived to interview their children.

"You'd be going into a home where everything is ticketty-boo and going along nicely," said the retired detective.

"Then you throw a hand grenade under the door."

Eastern Daily Press: Police cuff a shirtless David Wilson, before he is led away to be interviewed about his crimesPolice cuff a shirtless David Wilson, before he is led away to be interviewed about his crimes (Image: National Crime Agency)

Norfolk Football Association, the grassroots governing body for the sport in the county, said Wilson was suspended with immediate effect after police informed it he was under investigation for "allegations of inappropriate actions including potentially grooming children".

One senior official said: "The FA imposed the suspension in December 2015 and it is still in place.

"Although the allegations in this case were severe and a suspension imposed, suspensions from participating in youth football activities are imposed for a number of reasons including police or other civil authority investigations, therefore this is not the only occasion where such a suspension has or will be imposed."

The FA said before being appointed in 2013, Wilson was subject to safeguarding training and checks it carries out before people are allowed to take part in activities with children.

"These would include an enhanced DBS check and attending a three-hour safeguarding children workshop," the official said. "Mr Wilson's record shows that these were completed.

"Mr Wilson was suspended from football activity from the very first police contact and remains suspended to this day."

If you have been affected by anything in this report then information and advice can be found on the Thinkuknow website. Links also include advice for parents, carers and professionals.

If you need help or support, contact the Samaritans on 116 123 or Norfolk and Suffolk Foundation Trust’s First Response helpline on 0808 196 3494. Both operate 24/7.

Alternatively download the Stay Alive app, if you are having thoughts of suicide or if you are concerned about someone else.