London's New Constituencies?

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The Boundary Commission for England recently released its 2023 Review of Parliamentary Constituencies. This review includes its proposals for changing the parliamentary constituencies in England. Under these proposals the number of constituencies in London will increase from 73 to 75.

This map shows the boundaries of the recommended 75 London constituencies. Some of the boundaries for these new recommended electoral areas are significantly changed from the existing constituency boundaries. You can respond to these new recommendations from the Boundary Commission during the consultation period, which lasts until 2nd August 2021.

On this map each of the recommended constituencies is coloured by its Polsby-Popper score. The Polsby-Popper test is a mathematical formula for calculating how compact an electoral district is in order to detect for possible gerrymandering. The general assumption is that the more compact a constituency is the less likely it has been gerrymandered.

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On the map the lightest coloured constituencies have the highest Polsby-Popper scores. This means that they are the most compact. Bethnal Green and Stepney is the most compact of the new constituencies. This means that Bethnal Green and Stepney is the least likely constituency in London to have been gerrymandered in favour of one political party over another.

Only six constituencies in London have a Poldby-Popper score over 0.5. These six constituencies with the highest scores are Bethnal Green & Stepney, Croydon East, Fulham & Chelsea West, Walthamstow, Westminster & Chelsea East, and East Ham. The closer to 1 an electoral district scores then the more compact it is. Therefore these six constituencies are the least likely to be gerrymandered.

The five constituencies with the lowest scores are Brent Central, Hornchurch & Upminster, Mitcham & Morden, Croydon North, and Greenwich & Woolwich. These are the least compact constituencies.

The Size of Constituencies

The Boundary Commission is bound by law to ensure that every proposed new constituency contains between 69,724 and 77,062 Parliamentary electors. Because of the population density of London boroughs this means that all the largest proposed contstituencies in London (over 40km2 in area) are on the outer borders of the capital.

The five smallest of the propsed new constituencies (under 8km2) are all located in central London. It may be coincidence but the smallest of the proposed new constituencies, Bethnal Green and Stepney, is also the most compact.

Political Parties

Purely for fun I've attempted to predict which political parties are most likely to win each new proposed constituency, based roughly on which party is currently holds the present seats in London.

Colour by Political Party.

red = Labour
blue = Conservative
yellow = Liberal
grey = too close to call

Based on my unscientific guesses on how each proposed consituency is likely to vote these are the average Polsby-Popper scores for each political party's constiencies:

Labour = 0.366791
Conservative = 0.3591855
Liberal = 0.3221368

In other words there is very little evidence that the Boundary Commission is trying to gerrymander London's constituencies in favour any of the three main political parties.


The Boundary Commission's proposed new London constituency boundaries are available for download here.

London's New Constituencies? was made by Maps Mania.