MIG wrote:

My objection would not be how long it takes, but that it's the wrong
project. I don't understand why an orbital railway is such an
important goal. Well, I do. It's a way for a politician to make his
mark an a more obvious way than any general improvement in transport.

An orbital route might be a nice to have, but only in addition to the
radial routes, not replacing them.

An orbital route is a very good thing to have. London is teaming with
radial transport, there's very little that goes round!

The North London Line as it is at the moment is too infrequent and
passes too many radial tube lines without connecting to them