The knock came just before dawn. Helen's husband, Robert stumbled out of bed to answer the door – when he didn't return, she ventured down herself, to find him collapsed on the stairs. One of the plain-clothed police officers gathered in the hall showed her their search warrant.

"[Robert] just kept saying 'I'm sorry, I'm sorry'," she recalls.

"I was left in no doubt that whatever they had come for, he had done."

Grandparents-of-two in their 60s, the couple had been married since she was 18. She had only just joined him in retirement when their family was riven by what she can only describe as "an earthquake". Its aftershocks are still being felt.

Advertisement

It's unclear how Robert appeared on police radar, but after an exhaustive, humiliating search of their home – "he told them where to find what they were looking for, but they went through everything, even my underwear" – he was charged and eventually sentenced to two years in prison for possession of images of child sex abuse "in the thousands".

The national picture is obviously murky, but by any available measure, this is one of Britain's fastest-growing crimes. Government figures released late last year revealed a 700 per cent increase in the number of indecent images referred to law enforcement agencies since 2013.

Police now arrest an average of 400 people every month for viewing child abuse material. Most are men, but confound other stereotypes.

"We see men of all ages and backgrounds, family men and respectable professionals," said West Yorkshire police assistant chief constable, Catherine Hankinson. The 149 adults they arrested last year included four company directors, two solicitors and four tech professionals.

Some seem to consider themselves perpetrators of 'victimless' crimes – and while sharing an image of someone under the age of 18 carries a maximum prison term of 10 years, the sheer scale of the problem means fewer than one in four of the 2,528 people sentenced at crown court last year received a jail sentence.

'It's the gateway'

Police chiefs recently suggested the "horrifying" surge in numbers should prompt a national debate about whether men viewing images of child abuse should face prosecution or be given counselling – an attitude that solicitor general, Robert Buckland is keen to counter.

"It's the gateway," he told the Telegraph, last month.

"It can lead on to more horrendous crimes. People are making money out of this, children are being abused [for these images]."

Then there are the invisible casualties of these crimes: offenders' own families, who with the recent rise of vigilante 'paedophile hunters', live in constant fear of reprisal.

"The spotlight is often put on wives and partners: 'surely they must have known? I would have known if my husband was doing this'," says Deborah Denis of the Lucy Faithfull Foundation, a charity dedicated to preventing child sexual abuse. "It leaves them incredibly isolated because they often don't feel they can talk to even their closest friends or their family."

Last year in Britain 2528 people were sentenced for downloading indecent images of children.
Last year in Britain 2528 people were sentenced for downloading indecent images of children.

For Helen, the discovery was akin to a bereavement. "I felt very much like a widow," she says. "I went through huge grief, you almost feel as if he died." The length of Robert's sentence was a reflection of the volume and nature of the images in his possession. She was devastated to discover that some featured infants younger than the couple's then pre-school grandchildren.

Driven by competing, desperate needs to talk about the impact of what her husband had done, yet conceal her identity, she agreed be one of two wives followed over 12 months by Channel 4 for a remarkable documentary, Married to a Paedophile. ("Though I don't like the title," she would like to make clear.)

In a TV first, actors seamlessly lip-sync the women's real-life audio accounts to startling effect – allowing their rarely-heard perspectives to be delivered in familiar, Aga-filled territory.

'I've loved him for 44 years'

Helen's story is at times hard to understand, as we see her attempts to forgive the man she still loves, for crimes she can't countenance. "I've loved him for 44 years," she explains, "you can't just switch that off."

She's not sure the documentary fully conveys the anger she felt – "I would be shaking; how could he have done that?" – but it seems to have ebbed and flowed, in waves.

"I'm very clear that I hate what he did, but I don't hate the person," she says. "I was afraid all the way through that he would commit suicide. That was my biggest fear on the day the police took him away." She had to call their two sons to break the news. "I wasn't sure I was ever going to see him again."

Though she still struggles with the extent of Robert's betrayal, she believes his behaviour was symptomatic of depression: "We'd lost a lot of close family members, quite unexpectedly; we lost children ourselves and that was very difficult for us; he got made redundant. He was very, very bitter about that. He ended up a very angry man."

She visited him in prison every three weeks – which she sometimes saw as "dates" – and sent regular emails and photos of their chickens; he wasn't allowed to receive pictures of the grandchildren.

Robert was released last year after serving eight months, placed on the sex offenders register for 10 years and given a sexual offences prevention order, which means he is subject to monitoring software on all internet-enabled devices, including his phone, and random spot-checks by police.

Crucially, under the terms of his release, he is not allowed to stay the night alone with his grandchildren. Helen looks after them regularly in the family home, so she rented him a flat a few minutes' drive away – "just far enough that hopefully no one will know him."

Though there are no legal restrictions on him seeing the grandchildren otherwise, his daughter-in-law has so far prohibited it altogether. "There are some details that came out at the trial that she is absolutely haunted by," Helen says. "One of the videos that he looked at was of a breastfeeding baby who was taken from his mother [and abused]."

once the cameras stopped rolling, she and Helen's son have separated over differences in their reactions to Robert's crimes; the family fissured even further.

For her part, Helen seems haunted by the dots she might have joined over the years: she had known Robert had an interest in adult porn for most of their marriage, and he had always been something of a hoarder, but it never crossed her mind that the two would coalesce in such a terrible obsession.

"I said to him, 'I know you're going to look at [porn] but I don't want to know, don't show me'. Later on I agonised, did I give him permission? Had I been a better wife…" she trails off. "I've learnt it's a very common feeling."

The couple are now officially separated, but still see each other daily, and have no plans to divorce.

"I still feel married," she says. Besides, "I don't think I would ever fully trust someone ever again. If he could do it, I can't believe any man is trustworthy. I went through a painful phase of looking at each man that I met – 'do you do it? Do you?'."

* Some names have been changed