In order to ascertain the exact location of the old house it was decided that a datum point would need to be established to which all further measurements and orientation could  be related. As a cross-reference it was also felt that it would be useful to employ landmarks that existed both at the time and which are still visible on maps of the area as it currently stands. From a study of the available maps it was concluded that the critical datum point to establish was that defining the exact location of the southwestern tip of the old house plot as it was when the house was still standing as this could still be accurately observed on later maps once the house itself had been demolished and by which time a metric Ordnance Survey (OS) mapping system was in use such as those at the scale 1:1250. This meant that a reference point could be  established on a contemporary map and, with a knowledge of the size and orientation of the old house from earlier plans and utilising other corroborating methods, the exact position could be determined.

Above - an extract from the Ordnance Survey (OS) map revised in 1913-14 and published in 1916 at a scale of 1:2500

Above - Rillington Place shown on an OS map described as "corrected at 1935"  at a scale of 1:1056. The marker denotes the datum point set as the southwestern corner of the plot for the house at no. 10

NOTE: These earlier maps  depicting Rillington Place when it was still standing were drawn to a scale of  1:2500 or 1:1056 - slightly larger than the more modern ones which are 1:1250 - and so it is not an easy matter simply to superimpose one directly upon another. This, it is submitted,  has led other writers on the subject to conclude that the location (and size) of the house is somewhat different from that which is actually correct.

Next, it may be useful to consider the position of the chosen datum point in relation to a picture of the house itself taken by a press photographer at the time that the events there were being investigated: