Double junctions are avoided because the flat crossing of the outer turnout route over the inner through route is more maintenance intensive than two additional switches, and it includes a short length of unmaintainable plain line in the sixfoot... #RailwaysExplained https://twitter.com/shuntingwest/status/1259986071720464384">https://twitter.com/shuntingw...

(I deleted the original version of this tweet because it turns out that signalling is an eternal black magic to me. STICK TO PWAY, DENNIS.)

But, and this is why I love twitter, there is now a string of signalling folks adding lots of useful information underneath this thread!