Dog fighting is as secretive as it is barbaric.

The people behind the illegal bloodsport carefully conceal their identities, fearful of arrest and prosecution.

However, one dog fighter's IT mix-up led an undercover BBC investigation to unmask some of those involved in one of Europe's largest dog fighting networks.

The BBC has tracked fighting kennels to unlikely places in the UK – from a busy housing estate to the grounds of a stately home.

A simple mis-click from one member of a top-secret online dog fighting forum exposed the brutal reality of today's dog fighting.

The leak revealed graphic match reports documenting fight after fight, injured animal after injured animal.

A vast haul of intelligence was quickly harvested by the animal welfare charities, the League Against Cruel Sports (LACS) and the Ulster Society for the Prevention of Cruelty to Animals (USPCA).

That was the first glimpse of a highly secretive international dog fighting syndicate - one which the BBC has spent the past six months investigating and exposing.

I can't really put into words actually, it was just golden, said Russ Middleton, a former police officer turned Head of Intelligence for LACS.

The law across the UK bans not only fighting, but also owning fighting dogs and training them to fight.

Russ Middleton described the network as one of the biggest in Europe. Following a trail of evidence hidden in pictures, posts, and videos online, the BBC exposed a network of illegal dog fighters that stretches from the UK, across Europe and beyond.

Jessica, a medium-sized black dog, was discovered during the investigation and is receiving care at a rehabilitation center in Amsterdam. Experts aim to rehabilitate her and others like her who have been subjected to this cruel practice.