Here's my idea for the
Agree that would be better if you could do it but it's not just houses around West Hampstead. You'd have difficulty with the varying track levels and threading through major road bridges etc. If you really wanted to do this, it might be more practical to look at an additional Belsize Tunnel bore that could cross all MML lines without conflict. Can't see that being affordable, although it could have some utility for cross London freight.
My alternative suggestion for a northern terminus for the proposed OG orbital would be a single track spur to Colindale from a new junction just north of Hendon with an intermediate stop for the Police College and Middlesex University. Where running parallel with the Northern Line the LUL tracks might need shifting over a little in places to make space for the new single line. The terminus at Colindale would ideally have two tracks for resilience; it would be south of Colindale Avenue, adjacent to the park. The precise location of the junction north of Hendon would be selected to maintain standage for freights waiting to join the MML slows at Silkstream Jn.
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