Why is the electoral map changing now?

The political map is routinely revised to ensure seats have around the same number of constituents, and today the Boundary Commission issued its latest plans for what the re-shaped electoral map might look like in England, Scotland and Northern Ireland - the plans for Wales have already been published.

ITV News Political Correspondent Romilly Weeks explains why the electoral map is changing, and what it could mean for the next election.

So why is the electoral map changing now?

The short answer is the population of the country has changed pretty dramatically since 2000 - when the data on which the last boundary changes was collected.  

The independent Boundary Commission, which decides on the changes, is obliged to make every constituency have a similar number of voters, between 69,724 and 77,062.

The population of London, the South West and the South East has increased at a faster rate than other areas, which explains the extra seats there and the loss of seats in Wales, Scotland and the North.  

Overall it's likely to hand the Tories a small electoral advantage, as there are new seats up for grabs in regions where they traditionally perform more strongly.  

Election analyst Professor Colin Rallings calculates that if the boundary changes had been in place at the last election it would have given Boris Johnson a majority of 90, as opposed to the 80 he won.   

So not huge, but not insignificant either.  

However, behind the data, there are significant individual dramas playing out.  

Some MPs are set to lose their constituencies altogether as they become merged into neighbouring ones.  

Even Cabinet ministers like Ben Wallace and Dominic Raab face a tricky decision to stay in the area they know and fight a very much more marginal seat, or try to find a safer one elsewhere.  

Shadow Chancellor Rachel Reeves is in a similar position.  

The Boundary Commission has already consulted extensively on the proposals, but as as we discovered when we went to Lancashire, for many local people who find their constituency reconfigured around them and the MP they have come to know affected, it raises some pretty strong feelings. 

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