We move fast as the sun sets over the River Severn. At this point, it's a race against time to get as much done before the orange light fades, plunging these fields near Tewksbury, Gloucestershire into darkness.

We're with Lynn Sawyer from the Three Counties Hunt Saboteurs (TCHS), an anti-hunting group that operates throughout Gloucestershire, Worcestershire and Herefordshire. Tonight, her and another member of TCHS are trying to disrupt the ongoing badger cull – a topic that's back in the news after video was published this weekend illustrating the cruelty of the process, with a culler seen shooting a trapped badger and the animal subsequently suffering for almost a minute before it dies.

As badgers are thought to be responsible for the spread of Bovine Tuberculosis (BTB) – which can be spread to humans through contaminated animal products – the culls were controversially introduced in Gloucestershire and Somerset in 2013, and have since been rolled out to over 21 areas across England. After the release of the video this weekend – the first evidence of how badgers are killed by cullers – Dominic Dyer, CEO of the Badger Trust, told the Guardian: "This war on wildlife has been carried out in secrecy by poorly paid contractors with no independent monitoring or concern for animal welfare or public safety."

Cullers – who require a license to kill badgers – in Gloucestershire are paid £50 per badger and are required to fulfil a minimum kill quota of 160, but thus far most have failed to do so. In fact, as it stands, the effectiveness of the cull has been negligible. Despite farming minister George Eustice claiming in September that the strategy is "delivering results", recent government statistics showed only a 2 percent decrease in BTB cases in cull zones (and a 13 percent increase nationally), despite over 19,000 badgers being killed in 2017. Critics argue that while badgers can carry BTB, the disease is more likely spread between cattle or by other mammals.

"Foxhounds spread BTB and go through badger areas – if it was spread so easily the countryside would be on lockdown," says Lynn, who defected from a hunting group in her twenties. Media attention centred on her sabbing activities led to Lynn losing her job as a midwife almost 25 years ago, and she has been a full-time animal rights activist ever since.

Lynn crouching in a field

In rural Gloucestershire, Lynn is checking badger setts for both signs of life and traps or bait points put out by cullers. The sabs know of thousands of setts in the area, but don't have the manpower to keep tabs on all of them.

"Back in the first years we would have teams of people out every night," says Lynn. "But as the years have gone on we've seen our numbers drop significantly. Now, we probably have 10 percent of the people we used to have working an area that's ten times larger."

Despite Lynn spotting some badgers in the area just days before, the first setts she finds now appear to be vacant – so, as night falls, we move on. This is the kind of time badgers will emerge from their setts to feed, meaning it's the perfect opportunity for shooters to begin their work.

We head to a farm where, according to an informant, a shooter frequently operates. "When we come across them they tend to just pack up and leave," says Lynn. "Sometimes you can chat to them a bit, but their gun licence could be at risk if they do anything." Safe in that knowledge, and armed with head torches and some thermal imaging scopes, we follow Lynn as she goes looking for men with guns.

There are two known setts in this area, both on private farmland. We have to be careful not to be seen as we climb a gate and make our way across an open field to where the setts are hidden.

It's pitch dark. We begin scanning the field with the thermal scope and spot some white dots at the far end. Seconds later, we hear noises to our right. We stand completely still in the dark and speak in whispers. Then the other sab spots something through her scope. Following her directions, we see two bright white figures near the hedgerow further up the field. These could be the shooters. Now, it is all about being seen. Lynn and the other sab turn on their torches and head towards the figures. It doesn't take long before we hear a car start and watch headlights speed off down the adjacent road.

We can't be certain, but we're pretty confident we might have just caught a shooter in the act. Lynn finds snuffle holes where we spotted the white dots, and where we saw the figures we find a gate. Just behind it is a stile that leads to a lay-by and the road we saw the car go down. Bingo.

We jump back in the car and speed off in the direction of another sett, hoping to catch up with the shooter. The sabs identify shooters by their number plates, and Lynn checks every car we pass. We finish the night by finding another healthy sett, but no shooter.

We get up at dawn the next morning, when cullers will be shooting what they've caught in their cages overnight. We jump in Lynn's car and head over to a farm that's home to at least one sett, and where Lynn had a confrontation with the farmer a week prior. Lynn parks the car far away from where she'd left it before, and we make our way through tall maize fields towards a clump of trees.

The badger sett we find is the largest we've seen so far. The spoil heaps alone are at least 5ft tall. Of all the setts we've checked, this is the only one that is definitely thriving.

A trap found near a badger sett.

Then we find something interesting.

Nestled up against a small tree, with no effort made to conceal it, we find a cage. The mechanism has been tied back, meaning it's not currently "live’" Badgers are creatures of habit and will instinctively avoid anything new in their environment. To combat this, cullers will leave cages open and baited for days, until they can be sure badgers are entering, before readying the trap.

Despite being an act of criminal damage, sabs would normally flatten the cage. This time around, Lynn hasn't brought the tools she needs, so the decision is made to leave this trap – and a second one we find while leaving – to be dealt with later.

"We need to get you out more often!" Lynn tells me as we make our way back to the car. This has been an unusually successful 24 hours of sabbing; now, the priority is getting away as quickly as possible without being seen, otherwise the cullers will simply move the traps and reset them elsewhere.