Renowned war surgeon David Nott has been in Ukraine, treating victims of the Russian invasion and training Ukrainian surgeons in the finer details of conflict-related surgery.
At a hospital in the east of the country, well within range of Russian rockets, the British surgeon calmly carries out a complicated skin graft, helping to save the leg of a woman who suffered catastrophic injuries in a Russian shelling attack. Midway through the procedure, Prof Nott turns to his assistant - a Ukrainian surgeon called Ivan and says: "Here, you do it."
For David Nott, one of the world's most experienced trauma surgeons, this is the culmination of a week-long trip to Ukraine, during which he and his team will have trained dozens of local doctors.
He has operated under fire in front-line situations around the world - from Syria to Yemen, Gaza to South Sudan and now in Ukraine.
This is Prof Nott's second trip to the country since the Russian invasion at the end of February. This time he is not just operating on victims of war but aiming to pass on some of his immense depth of knowledge and surgical experience.
"I know what it's like to be under fire. I know what it's like to be in an operating theatre which is being shelled," he says.
"You're trying to do your best to try and save the life of the patient in front of you. But what we can do here is train people and I think we will have trained 70 surgeons in six days."
Some of those attending the intensive three-day course run by the David Nott Foundation are front-line doctors, momentarily returning from the fighting in the eastern Donbas region.
One doctor admitted to the BBC that, too often, they do not have enough medical expertise or experience to keep people alive when they arrive at field hospitals with catastrophic injuries.
Others here are civilian medics, learning new skills, because their hospitals are full of people with new kinds of injuries.
For orthopaedic surgeon Oleksi Horehliad, the three months since the Russian invasion have almost been a case of sink-or-swim.
"It's very stressful, not only for patients but for doctors too," he says. "It's a horrible situation when you see these young guys with mangled extremities, with shrapnel wounds, with amputations. It's just a disaster for me."
The big draw at these courses might be Prof Nott and his years of experience, but the star of the show is Heston - a life-like medical dummy with 50 separate surgical procedures, replicating war wounds. Costing tens of thousands of pounds, Heston is part of a system that allows Prof Nott and his team to teach advanced life-saving skills.
He instructs the Ukrainian doctors in complex surgical techniques - such as how to deal with blood loss, how to quickly assess and stabilise a patient in the first few minutes, plastic surgery, and amputations.
Travelling across Ukraine has been tiring work for this group of veteran war surgeons. Their last destination is the front-line city of Kharkiv - battered by Russian shelling, with thousands of injured people being treated by over-stretched local doctors.
"It's really difficult and frustrating to not be able to help a patient because of limited resources, especially on the front line," says Ammar Darwish, a Manchester-based surgeon who has accompanied Prof Nott on surgical expeditions around the globe.
"In places like Ukraine or Syria or Yemen, you just need to concentrate on your patient and treat them, especially when you have mass casualties - it's very difficult."
As with the student doctor who helped out on the operation to save a patient's leg, the most rewarding thing for Prof Nott is that medics here are already putting complex techniques learned on his course into practise.
"It's been amazing," he says. "I've just had a message on my phone from a doctor who's done his first ever thoracotomy to save a patient's life by making an incision into the heart. That's thanks to the training he had two days ago. He's now back on the front line in Donbas under severe conditions. And he sent me a photograph to say, 'look what I've done, David, I've made the incision, I've done exactly what you've been teaching us.'"
The day after his return to the UK, Prof Nott is due back on shift in an operating theatre in his day job as a National Health Service (NHS) consultant - but he's already organising the next life-saving mission for the foundation that bears his name.