On a Saturday morning in July 2011, Nigel Lang, then aged 44, was at home in Sheffield with his partner and their 2-year-old son when there was a knock at the door.

He opened it to find a man and two women standing there, one of whom asked if he lived at the address. When he said he did, the three strangers pushed past him and one of the women, who identified herself as a police officer, told Lang and his partner he was going to be arrested on suspicion of possessing indecent images of children.

He knew he was innocent but was powerless to prevent what happened next, as over the coming days, weeks, months, and years, through absolutely no fault of his own, events took place that would cost him his health and his career, and put serious strain on his relationships with those he loved the most.

Lang described the arrest, and what followed, as "the most horrendous and horrific time of my life."

What makes Lang’s ordeal all the more shocking, BuzzFeed News can now reveal, is that his wrongful arrest, and all the consequences of it, stemmed from what police called a “typing error”.

He was told that when police requested details about an IP address connected to the sharing of indecent images of children, one extra keystroke was made by mistake, sending police to entirely the wrong physical location.

But it would take years, and drawn-out legal processes, to get answers about why this had happened to him, to force police to admit their mistake, and even longer to begin to get his and his family’s lives back on track.

Police paid Lang £60,000 in compensation last autumn after settling out of court, two years after they finally said sorry and removed the wrongful arrest from his record.

Today, six years after it first began, Lang speaks publicly for the first time about his “horrendous nightmare”, in part to help make sure that no one else has to go through what he endured.