The LNER Encyclopedia

These sites are interesting:

http://m.bbc.co.uk/news/uk-england-london-21333361

http://londonfirst.co.uk/our-focus/keep ... ossrail-2/

http://www.transportxtra.com/magazines/ ... /?id=25199

http://m.money.aol.co.uk/2013/02/05/12b ... -unveiled/

The AOL Money one mentions Hertford East as a potential northern terminus. I'll believe that when I see it since the double track section from Cheshunt Junction to Broxbourne Junction is a significant "pinch point" on the Greater Anglia network even now, never mind with additional services thrown in.

Sounds like a variation of the planned 1950s Chelsea-Hackney Underground link that was raised every so often. Lets hope that this time it might just happen.