The Green belt and the Underground

[AM9]

Of course, modern thinking is that commuter rail can preserve green belt areas by allowing travel to leap beyond them. Although not LU, there is surprisingly little development between Elstree and St Albans despite the presence of the MML, which owing to TL services is a very high capacity commmuter railway. I'm sure developers would love to spread Radlett village out until it is continuous housing along the old A5 (A5183).
Similarly, Theydon Bois remains a small settlement despite the frequent Central line service running between the country town of Epping and the northern end of the Roding Valler sprawl that is Debden.

 

[PeterC]

But for the green belt new housing might have made the extension from Stanmore to St. Albans viable. Its my understanding that the Metropolitan Railway was contemplating this and it explains why Stanmore station was built in a way that would have made an extension very easy.

Maybe the LMS Stanmore branch would have been extended further north too (and electrified)!

Possibly the Met's plan to extend from the present-day Watford station to Watford Central station would have come to pass. As it is, the site of the planned new station was already in railway ownership and might still be owned by TfL 'today' (I am unsure - no doubt someone else will know!)

Also, when looking at railways in North London its worth remembering that the Piccadilly Line would not have been so overcrowded 'today' had both the Northern Heights line to Alexandra Palace and the Palace Gates branches remained open. The latter went to Docklands via Stratford, and whilst admittedly not ideal for central London the way Stratford has changed in recent years (Olympic Park, Westfield, etc) would have made this service 'extremely useful'. This would have been an excellent London Overground service.

The LMS branch junction faced the wrong way on the main line for services to central London and a northern extension would have ploughed through an area fully developed before the war.