Dog fighting is as secretive as it is barbaric.

The people behind this 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).

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

The law across the UK bans not only fighting, but also owning fighting dogs, training them to fight, trading animals, and even filming fights without good reason.

'There was a whole range of different dogfighters in there, all collaborating, chatting, sharing videos. It gave us a real insight into the global perspective of dog fighting.'

Mr. 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 has been able to expose an organized network of illegal dog fighters - one that stretches from the UK across Europe and beyond.

According to experienced vet David Martin, dog fighting is much more common than people think, with evidence suggesting it occurs in every major town and city in the UK.

The BBC identified the man behind Boneyard Kennels, one of the most significant dog fighters, as David Patterson, a mixed martial arts coach from County Antrim. The investigation traced about 40 fighting pit bulls to his operations.

As the investigation unfolded, BBC journalists managed to infiltrate online platforms used by dog fighters. They even met with a member willing to sell a fighting dog in Amsterdam.

The undercover investigation has also spotlighted issues surrounding dog rehabilitation, showcasing efforts to help formerly fighting dogs recover and adapt.