Oh, you just couldn't make this up. Solid gold.
Thank you, universe, this is just the sort of hero story we needed on a Saturday.
The 41-year-old actor was passing through the area in an Uber with his wife when he spotted the incident taking place.
It all took place back in November, but details have only just begun to emerge.
He reportedly leapt from the back of the taxi to intervene as four muggers targeted a passing Deliveroo cyclist.
The drama went down on Marylebone High Street, just round the corner from Sherlock's fictional home on Baker Street.
WATCH: BENEDICT CUMBERBATCH CAN'T SAY THE WORD 'PENGUINS'
Deliveroo's staff do noble work, bringing food straight to the door of people who are too hungover to leave the sofa, so we're glad the thugs didn't get away with this.
Uber driver Manuel Dias told the Sun: "I was taking Benedict and his wife to a club - but I didn't know it was him at first.
"I went to turn down into Marylebone High Street and we saw four guys were pushing around a Deliveroo cyclist.
"My passenger jumped out, ran over and pulled the men away. They turned towards him and things looked like getting worse, so I joined in.
"He stood there instructing them in the street, shouting, 'Leave him alone.'
"It was only then I recognised Benedict. Then it all got a bit surreal. Here was Sherlock Holmes fighting off four attackers just round the corner from Baker Street."
Imagine what was going through the muggers' minds at this point. 'Are we dreaming lads or are we actually being battered by Sherlock Holmes?'
The Uber driver added: "I had hold of one lad and Benedict another. He seemed to know exactly what he was doing. He was very brave. He did most of it, to be honest.
"They tried to hit him but he defended himself and pushed them away. He wasn't injured. Then I think they also recognised it was Benedict and ran away.
"Benedict was courageous, brave and selfless. If he hadn't stepped in the cyclist could have been seriously injured.
"He asked the rider how he was and when he said, 'I'm OK,' Benedict just hugged him."
The newspaper reported Cumberbatch saying: "I did it out of... well, I had to, you know..."
A true hero walks among us.