I want to show you my maps. I like maps, don't you? They're such useful things when one wants to move about in a hurry. You'll like my maps.
The clue to the identity of the mysterious Dr Fell, the lodger in the Musgrave household, is the mention of a map. That he has a map in his room, marked with crosses, makes a connection with what the investigating journalist has read in Case Histories of Famous Crimes, volume 1:
No one ever saw Jack the Ripper except possibly his victims, none of whom lived to identify him. He was heard running away from the scene of his crimes on several occasions. As he ran, near-witnesses reported hearing a curious sound like a hiss. Apart from that the only other piece of evidence ever discovered was a fragment of a London street map. It was found in Whitechapel near the scene of his last crime.
I haven't found elsewhere any reference to the Ripper's map, and suppose it is an invention of Marjory Allingham's, who wrote the radio play on which the film is based, or else of the scriptwriter John Gilling.
We see Fell's map twice: when the young Miss Musgrave finds it in Fell's room, and later when he shows to old Mrs Musgrave. In the first instance we see the map quite well, and in a better print of the film it might be possible to see what is the place mapped:
As it is, the map's details are hard to make out. We can see that it is marked with crosses, but it is only later, when Fell identifies the places he has marked, do we know that this is supposed to be a map of a part of east London, centred around Whitechapel. A clearer map of the area can be seen in the 2001 Ripper-centred film From Hell:
From Hell (the Hughes Brothers 2001)
Like Dr Fell, the detective in From Hell has marked the locations of the murders on the map with crosses. Johnny Depp's markings don't seem to correspond to the real murder scenes, but then again Dr Fell, in Room To Let, is oddly amiss when he lists their locations:
I wonder if you recognise this, Mrs Musgrave: a byway off Spitalfields, Buck's Court. I made a cross there. Commercial Road. Old Brompton Road. I made a cross there. And look, look Mrs Musgrave: Miller's Court. November the ninth, 1888... Don't these names mean anything to you?
The date he gives is accurate and corresponds to the right place, Miller's Court, where Marie Kelly was murdered. At this point in the film we can be sure that Dr Fell is the Ripper, though this exact chronological match comes at a moment when the topographical matching has just broken down. Unless I have seriously misheard the place name (which is possible), Fell says he has committed a murder in the Old Brompton Road, on the other side of London, in a district that has no association with the crimes of Jack the Ripper.
There are at least two possible explanations for this lapsus. David Cairns at Shadowplay suggests that the actor Valentine Dyall didn't bother to read the script, only his own lines, so perhaps the reference to the Old Brompton Road was an erroneous interpolation on his part, left uncorrected by the director. Alternatively, the topographical incoherence could have been intended by the author or scriptwriter as a signal that the story of Room To Let is not seriously proposed as an explanation of the Jack the Ripper mystery.
In Room To Let there is a topographical incoherence of a different order. The chief setting is the house in which Dr Fell comes to lodge:
The location for the front of the house is 23 Pembridge Square, W.2:
Google Street View, April 2012
The back of the house, however, is an entirely different type of building:
This is Oakley Court, Bray, an early production base for Hammer films, before the company moved to Down Place, just next door. It is now a hotel:
The interiors at Oakley Court were used in Room To Let, even though they seem far too spacious for a town house of the Pembridge Square type. In Man In Black, a Hammer production from 1949, Oakley Court represents what it is, a Victorian Gothic country house:
The interiors of the house in Room To Let can be recognised in Man In Black:
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There are two other maps in Room To Let:
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(I think this is the same globe in two different rooms.)