The Area Maps and Tables each cover a specific geographical area, rather than a fixed set of constituencies (as is the case for the Constituency Charts and Election Results Tables).

• For a given geographical area, usually comprised of one or more local government districts which contained in 2010 a whole number of undivided parliamentary constituencies, the map is divided into unique sub-areas, each of which has a unique different history in terms of which constituency it has been in since 1885.

• Each sub-area is denoted by a different letter (firstly lower case, then if needs be upper case, and for some, Greek letters).  If a sub-area is split into non-contiguous parts then these are denoted, for example, as b', b'', etc., as necessary.  In drawing these sub-areas, boundary changes which do not affect any electors or at most just one complete street are not reflected on the map - the Area Map would use the most recent boundary in such cases.

• The table which accompanies each map shows the constituency history, with constituencies colour coded, so that the same colour does not apply to more than one constituency on each table, and the same colour is used when a constituency appears in more than one table.

• The far right hand column of of each table gives an estimate of the 2010 electorate in each sub-area, expressed as a percentage of the 2010 constituency size (to the nearest whole percent).  Sometimes a sub-area's electorate percentage estimate is shown as 0 - this just means that it is estimated to be less than 0.5%.  The whole number percentages always add up to 100% for the 2010 constituencies.  The sub-area size estimates have been derived using a methodology based on the electoral changes between constituencies shown in the Media Guides that have been published prior to the 1983, 1997 and 2010 General Elections.  This provides estimates of sub-area sizes for changes going back to the February 1974 General Election.  For sub-areas defined by changes happening earlier, this website's author's own estimates are used.

By way of an example, in the Westminster & City of London Area Map and Table, the sub-area around Bayswater, is named sub-area a.  From the table it can be seen that this sub-area was in Paddington South from 1885 to 1974, in Paddington from 1974 to 1983, in Westminster North  from 1983 to 1997, in Cities of London & Westminster from 1997 to 2010, and finally back in Westminster North from 2010 to now.  It is estimated that sub-area a contains 17% of the electorate in the 2010 constituency Westminster North.

Minor changes resulting from interim reviews carried out by the Boundary Commissions between the main periodical reviews are generally not shown.  A few exceptions are made where such changes are more substantial (e.g. Milton Keynes 1992, Oxford 1964).  Sometimes the boundaries shown are those revised by the interim review, especially if these were in force for more elections than the original.