Three British rockets streaked into the sky towards Russian forces under attack in a key frontline town in eastern Ukraine.
The target was a mobile Russian command post. A Ukrainian artillery officer said it would have been hit because his soldiers never miss.
Sky News is the first to be granted permission to film a multiple-launch rocket system given to Ukraine by the UK in action during the war and to meet the soldiers operating it.
"Thanks to these weapons, we've carried out really high priority missions," said the commander of the artillery unit, who asked to remain anonymous for security reasons.
This included hitting military bases, columns of armoured vehicles and ammunition stores.
UK and German weapons responsible for 30% of Ukraine's success in the east
The commander said, in his opinion, around 30% of the successes achieved by Ukraine in a major counter-offensive in the east were thanks to British, as well as German, rocket launchers.
"This is one of the key factors, which influenced the Russian army not just to retreat, but to run," the officer said, referring to the recapture in recent weeks of swathes of illegally-occupied territory across Kharkiv region and into the Donbas.
Sky News was granted exclusive access last week to soldiers operating one of six M270 Multiple-Launch Rocket Systems (MLRS) that Britain has given to Ukraine.
The commander and a number of his men also received training in the UK on how to operate the system.
"I want to say thank you to all officers, sergeants and instructors who took part in our training, because it was so powerful," the officer said.
"They gave us a lot… Thanks to the training, only three days after returning from England we were already carrying out missions."
Hidden in a line of trees in the middle of sprawling fields, the dark green contraption - the size of a large pickup truck on a set of tracked wheels - was deliberately hard to find.
We were not allowed to reveal the location nor the true names of any of the soldiers we met.
Ukraine's limited number of long-range artillery pieces make them a prime target for Russia.
But the mood among troops at their makeshift base under the trees seemed pretty relaxed.
They were just exhausted having worked through the night and into the day, conducting "fire missions" against Russian targets as part of a Ukrainian advance on the town of Lyman.
Rocket launcher doubles up as mobile home for soldiers
We met the unit on 29 September. The town was recaptured by Ukraine two days later.
One of the soldiers, who his commander named as "Ghost Rider", showed us around the rocket launcher, which loomed over him, framed by orange-coloured autumn leaves.
It is a mobile home as much as a war machine, with the servicemen eating, sleeping and fighting from inside a cabin built at the front.
Dotted around a steering wheel, control panel and computer screen was a tin can of bacon, a slumped rifle, even an air-freshener attached to a wire in a corner on the ceiling.
There were also tell-tale signs of the rocket launcher's British owners and American manufacturers, with panel instructions such as "fire extinguisher" and "turn indicator" in English.
The long, green missiles, stored on a large rectangular-box-shaped launcher, sit behind the cabin, making the weapon completely self-contained.
Three soldiers operate the system, one giving commands, another ensuring the coordinates for the target are correct on the inbuilt computer panel and a third driving.
Asked how he felt when he fired the launcher, knowing he was attacking Russian positions, Ghost Rider, a young lieutenant, said: "After launch, the first feeling was my heart like this - boom, boom. That's all. And then everything was calm."
Men on duty 24/7 for month-and-a-half
This unit of artillery men and engineers has kept the weapon operational and on the move 24 hours a day, every day for the past month and a half.
It's not easy. In service since the First Gulf War back in 1990 to 1991, the system is often in need of repair and their headquarters can call at any moment to order a strike.
By the time we joined the team on 29 September, they had already carried out six operations over the past 24 hours, with minimal sleep, launching around 50 rockets.
The artillery commander, whose unit operates the six British multiple launch rocket systems as well as three German MARS II launchers, said they only go after high-value targets.
Their missile-supply is finite, so the Ukrainians need to be selective.
It is also about quality rather than quantity.
The missiles fired by the British system - Guided Multiple Launch Rocket System munition, or M31A1 - are precision-guided, with a range of more than 50 miles (80km).
It means they are highly accurate. This also reduces the potential for civilian casualties.
In contrast, much of Russia's artillery systems - and the Soviet-era launchers previously used by Ukraine - must bombard a target with a barrage of rockets to ensure it is destroyed, requiring much more ammunition and causing a lot more collateral destruction.
As we waited with the soldiers, a missile resupply arrived.
A large vehicle with a mini crane rolled into sight along the treeline. It lowered several missiles - each with M31A1 written in white on the side - for them to be slotted into the MLRS.
'Fire' shouted in English
Minutes later, the team received a strike order. It was the mission to target the mobile command post.
The operators scrambled into their cabin and drove the giant weapon out of its leafy shelter. A tree branch jutted out of one side - remnants of the camouflage.
They headed to a field, the tracked wheels enabling the team to travel with ease and at a decent speed despite the muddy ground.
Firing spot chosen, the launcher was slowly pointed diagonally upwards. It made the same kind of grinding mechanical noise as a forklift truck being raised.
Target locked, a commander in the cabin said "fire" in English, a switch was flicked and the rockets were launched.
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The team then needed to move away quickly because of the possibility of Russian forces working out where the artillery came from and returning fire.
The whole process, from aiming to firing, is done in a couple of minutes - American operators in the past have coined the phrase "shoot and scoot". The weapon is also nicknamed the "70km sniper rifle" - a nod to its range and accuracy.
Back under tree cover, the unit waited once more for instructions.
After about three hours of standing around, checking an encrypted device used to receive instructions, a Ukrainian Humvee churned into view through the undergrowth. It was part of a force tasked with protecting the system.
The soldiers chatted, then another firing mission came in and out the rocket launcher rolled.