The trooper, in his 30s, was in the Parachute Regiment before joining the SAS.
A source said: “He’s the toughest of the tough with a chest full of medals to back it up.
“During a series of war tours he has built up an impressive body count – there are few who would be better trained and prepared for what unfolded in Kenya this week.
“He’s a supreme fighter and took real pride battling alongside his Kenyan comrades.”
Suggestions the SAS trooper was out “running errands” when the attack unfolded were scotched by well-placed insiders last night.
A source said: “He was mobilised along with Kenyan RECCE Special Forces commandos – he was not out shopping.
“This guy is elite, he’s the closest thing to Superman we’ve got, but he doesn’t get changed in a phone booth and he doesn’t keep a glock pistol, heavily modified Canada Colt C8 assault rifle with a silencer and a combat dagger in the boot of his car when he goes shopping – that gear is kept on a secure base.”
The unnamed soldier was photographed storming into Nairobi’s DusitD2 hotel and office complex while it was under attack by terrorists.
He was in the country training Special Forces when news of the atrocity broke.
Jihadists from Somali-based al-Shabaab killed 21, including Brit Luke Potter.