The inquest heard Guardsman Janes was wearing body armour
A British soldier was killed and three others injured during an ambush in Afghanistan, an inquest has heard.
Grenadier Guardsman Jamie Janes, 20, of Brighton, was fatally wounded in an explosion while on foot patrol in Helmand province in October.
The Brighton inquest heard the soldiers were attacked in an area covered by improvised explosive devices.
The coroner ruled Guardsman Janes was unlawfully killed while on active service.
Brighton and Hove coroner Veronica Hamilton-Deeley said Guardsman Janes and his colleagues showed "selfless heroism".
She added: "I have held hundreds of inquests over the years but I have rarely, if ever, come across such selfless heroism as has been exhibited by all the people who fight in theatres, like Afghanistan, particularly the men I have heard from today.
"As for Jamie himself, he too acted heroically, he was a hero."
The inquest was told the troops were trying to stop the area, which had been virtually deserted by local Afghans, becoming an insurgent-occupied territory.
Major Richard Green, patrol commander, said it became apparent that it was more than just locals watching and one guardsman fired warning shots and flares to move enemy forces on.
He added: "The patrol was under no illusion that if the situation was to worsen, then we would come back and look at it another day, and that's the situation we got to just prior to the explosion.
"The explosion then took place and it was very apparent, very quickly that it was a significant event. We hadn't worked out what had happened but it was clear that the situation was deteriorating rapidly.
"Very quickly, within seconds, probably minutes, a lot of small arms fire, including rocket-propelled grenades, were starting to rain down on the guys on the patrol.
"We had worked out that there were very serious casualties and we worked out that Guardsman Janes was the worst of the group. We then requested the support of the medical emergency response team."
He was airlifted to a hospital at Camp Bastion where he was pronounced dead.
Brighton Crown Court was told Guardsman Janes had a rifle and a pistol and he and his comrades were wearing body armour, including helmets.
Lieutenant Colonel Roly Walker, commanding officer of 1st Battalion Grenadier Guards, said: "Jamie was an experienced young soldier and his talents shone through to all of us.
"He willingly took personal risk to make others safer and made the ultimate sacrifice."
His mother Jacqui Janes, who attended the inquest, was previously in the news after Gordon Brown sent her a handwritten letter of condolence following her son's death.
She criticised Mr Brown for apparently misspelling Guardsman Janes name as "James" and other errors.
Ms Janes spoke to Mr Brown on the telephone and later accepted an apology following a press conference.
Following the verdict she said: "All I want to say really is that I do believe that all the boys that Jamie was with did everything that was humanly possible."