Looking at the legend, it seems that London is key to 3 or 4 bonuses. By making it harder to capture London initially it makes all of the bonuses harder. It is similar to why some of the resources in AOR 2 start with 5 and others start with 2.
I can help with that- England have only 3 territory and worth 2(if you take cypruys then worth 3 for 4 territory),these is very big bonuses,and that why london worth 6 neutrals(almost forget london give you +1 autodeploy) These mean that England with cyprus give +4 for 4 territory,and that why is london have 6 neutrals,because will be much easy to someon get bonuses ,expecialy if you have great drop on begining of game.