Mornington Crescent

I was trying to explain Mornington Crescent to Noemi this evening, and not having a copy of N. F. Stovold’s "Mornington Crescent: Rules and Origins" to hand it's proven rather tricky.

I thought that a simple example "Baker St - Oxford Circus - Grange Hill (I didn't want to get into Central line quartering too soon, so I thought that G.H would be the least confusing stop there) - Hackney Central - Neasden - Dollis Hill - Marble Arch - Dollis Hill - Victoria - Chalk Farm - Morning Crescent" would do nicely, but - and I'm sure you appreciate the dilemma! - how can one explain to a beginner the need to avoid lateralisation in a Northern elliptical approach?

Yes, I could have chosen an even simpler example, but surely the understanding comes from seeing how it all works in practice rather than just theory?

If anyone could give a neat illustration of a bisected conical inversion around Paddington I'd love to hear.

Thanks...