As they reportedly shouted "This is for Allah", the 47-year-old decided he would shout back, and screamed: 'F*** you, I'm Millwall'.
The terrorists then left to attack neighboring pubs before police marksmen shot the group dead.
Roy, of Peckham, South East London, said: "Like an idiot I shouted back at them".
"The three of them, I'm fighting them, and at the time I'm thinking of those families and kids who need to get out of the bar".
'It was just me, trying to grab them with my bare hands and hold on.
"I was on my own against all three of them, that's why I got hurt so much", he told the website.
The "Lion of London Bridge" nickname is a reference to Millwall's nickname, the Lions. In any case, Larner, who admits he'd had "four or five pints" at the time, punched and fought with all three attackers while the rest of the patrons ran for the rear exit. Everyone else ran to the back. They got me in my head, chest and both hands. "There was blood everywhere", he said, while sharing that doctors estimate he'll remain hospitalized for the next week. Although two of the men did get past him, he held one up for 20-30 seconds.
The club has often been associated with football hooliganism, particularly in sections of the press, although many fans argue this is unfair, given almost all clubs have this element of support. OK I got a good hiding from it, but they're not alive, I am still'.
One of those to visit Larner in hospital was Mick Church, who paid tribute to "a true fearless Millwall man through and through who helped so many Saturday now needs help himself" in the comments on the fundraising page.
A petition to honour Larner with the George Cross medal for heroism has been launched, while Millwall Football Club have praised the supporter for his "immense bravery". That certainly seems to apply in this case.
Larner is recovering in hospital and has apparently sent a Facebook message via another user (see below).
Larner is expected to be in the hospital for another week.
And then, in a moment that Roy will surely regret once he leaves hospital, he said: "If you're looking for a minder, Piers..."