Thain was a thirty-four year old constable from Suffolk who seven years previously had been a police officer on the Woolwich docks. His beat on Friday 31 August 1888 was a thirty minute circuit which took him along Brady Street, passing the corner leading into Buck’s Row. He did see “one or two” workmen walking along Brady Street. At about a quarter to four in the morning he was alerted by PC John Neil (97J, Bethnal Green), who was in Buck’s Row as he passed, to the presence there of the body of a dead woman. Shortly after joining Neil the two were joined by PC Jonas Mizen (56H, Whitechapel) who had been informed that a woman was lying on the road by Charles Allen Lechmere (who gave his name as ‘Cross’ at the inquest) and Robert Paul. Neil dispatched Mizen to Bethnal Green Police Station for the police ambulance, and Thain to bring Dr. Llewellyn from his surgery on the Whitechapel Road. Thain returned with the doctor about ten minutes later to discover that PC Neil had been joined by two workmen at the body.
Once the doctor had conducted an examination of the body at the scene he instructed that the body be removed to the mortuary. John Thain assisted the other officers in lifting the body from the road and placing onto the ambulance. In the process of doing this Thain discovered that the back of the body was saturated in blood, and he got blood on his own hands at this point. Thain did not go with the ambulance to the mortuary but kept watch at the place where the body was discovered until the arrival of Inspector John Thomas Spratling (J Division, Bethnal Green). Shortly following the arrival of Spratling Thain began a search of the surrounding area but uncovered nothing suspicious. We know that Inspector Spratling made his way to the mortuary to examine the body of the deceased.
Constable Mizen was on the beat at the east of Hanbury Street, at the crossing of Baker’s Row, in the process of dispersing drunks and vagrants, when somewhere between a quarter and ten to four in the morning (Friday 31 August 1888) two carmen informed him that a woman was lying on Buck’s Row and that another policeman requested his presence there. Charles Allen Lechmere (who gave his name as ‘Cross’ at the inquest), one of those carters, refuted this statement saying that they saw no other policeman. When Jonas Mizen arrived on the scene PC John Neil (97J, Bethnal Green) was already at the body of Mary Ann Nichols. At this time they were joined by another constable, John Thain (96J, Bethnal Green), who came from Brady Street. It is evident that Neil has taken charge of the crime scene and dispatches Mizen to collect the police ambulance from the Bethnal Green Police Station, and Thain to get Dr. Rees Ralph Llewellyn from his surgery at 152 Whitechapel Road, not three-hundred yards from where the body was discovered.
The Bethnal Green Police Station (J Division) was on Ainsley Street, on the corner of the Bethnal Green Road. The current location of Bethnal Green Station on Victoria Park Square, facing the Museum Gardens, was at that time the Drill Hall of the Tower Hamlets Engineer Volunteers. At the time of the Whitechapel murders, as is evinced by the letter of Superintendent James Keating (Saturday 13 October 1888), the station was no longer thought fit for purpose and new premises were being sought. This station is a fifteen minute walk from Buck’s Row, and so PC Mizen would have been absent from the scene for at least half an hour. Once he was back on the scene with the ambulance, and when Llewellyn had conducted his preliminary post-mortem examination, at the instructions of the doctor the police removed the body to the Old Montague Street Mortuary which was no more than a brick shed in Pavilion Yard. This was accessed through a gate at the bottom of Eagle Place, off the northeast end of Old Montague Street. At the closing of the inquest on 22 September the Coroner made some remarks on the need for a mortuary in Whitechapel. It is altogether likely that all four policemen (Sergeant Kirby had joined them on Buck’s Row) accompanied the body to the mortuary, where they were joined shortly afterwards by Inspector Spratley of J Division.