A colourful character, Don tucks his footstool under one arm and pulls his old shopping trolley along with the other hand as we head for Jewry St, near a church then known as the prostitutes' church. He explains that one reason the police took their time realising that they had a serial killer on their hands was that the City of London and Scotland Yard had their own territory and neither was interested in working for the other.
But on September 30, the Ripper struck twice, once in the jurisdiction of each police force, and then the hunt began in earnest.
Standing near Mitre Park, a spot that would become known as Ripper's Corner, there's an anxious atmosphere as people look towards the deathly doorway that our guide indicates and then, in many cases, over their shoulders. There seems something evil about the place.
"The salesman returning home with horse and cart prodded the bundle that the horse shied away from."
We wait for what comes next, but Don gets a laugh as he tells how the man thought the bundle to be his drunken wife, until he checked the doorway.
We learn that police patrolled this area on foot every 15 minutes. It suited the women to be quick for their three pennies but, unfortunately for them, their demise was even quicker. Strangle, suffocate, cut. The Ripper's method was swift. He attacked mostly on Friday and Saturday nights, these being quiet once the weekday markets closed and this Jewish area being fairly empty on the Sabbath.
Then we're off again, a crowd of young and old, all types, trundling along the darkened streets of London's East End behind the man with the wispy hair shifting in the breeze who leads us Pied Piper-like to our next destination.
We stop on Cutler St where Don explains that we will now be moving into the old quarter, where humans shared their accommodation with pigs and chickens and where many children died before the age of 5. It's a colourful area apparently, Don telling us how he's looked up at windows here and seen modern-day prostitutes dancing and miming the events he narrates.
We learn about an anti-Jewish inscription scrawled in a doorway and how police thought the clues suggested a Freemason. But Police Commissioner Charles Warren ordered the inscription rubbed out in case it stirred racial hatred. And today? Well, it's the Happy Days Chinese restaurant.
We hear gruesome details, such as the package arriving at the police station with half a kidney, said to be that of victim Catherine Eddowes who'd been killed at Mitre Square. But there was no fingerprinting or DNA testing back then.
Passing the Catholic Church building used for the poor where victim Mary Kelly was known to have stayed, our next stop is Spitalfields, which back then was a fruit and vegetable market.
It was here that one of the victims came, Annie Chapman, not feeling well after being kicked by another prostitute, but nonetheless needing a customer.
Don tells us that "many people saw a man ask her 'Will you?' to which Annie replied "Yes". When they found Annie's body on September 8 her womb had been cut out with a 12-inch knife.
The 2001 Johnny Depp film From Hell, on which Don consulted, featured the pub called The Ten Bells as the one frequented by Jack the Ripper and many of the prostitutes. Local drinkers seem accustomed to Don's visits with a 100-strong entourage, hamming it up and posing lewdly for photographs. We remain, safely, on the other side of the street.
Turning the corner, we enter Dorset St, in 1888 the "worst street in London" where 1500 people slept every night. In a building here lived Mary Kelly, the girl from the Catholic shelter. Some in the street heard cries from Kelly's room and thought it only passion, but it was the Ripper and he had more time to work.
On November 9 the landlord discovered the corpse, with Mary's body and face having been skinned.
After this there were no more killings, causing everyone to wonder why.
Don discusses the various suspects put forward by the police and why each one seemed unlikely.
Finally, reaching into that old-style shopping trolley that he's hauled through the streets of the East End, Don produces something for those wanting more. His book, in which those truly intrigued by the dark past can learn every detail from the ex-policeman who himself has become something of a legendary figure when it comes to the horror of Jack the Ripper.
CHECKLIST
Details: Jack the Ripper Haunts with London Walks, every night (except December 24 and 25) at 7.30pm from outside Tower Hill tube station.
Further information: See visitlondon.com.
The writer was a guest of London Walks.