In London the easy bits of the 'swiss cheese' were tunnelled through first. Hence North London where the easy clay is in greater abundance has the earlier and more extensive tube trains (and more expensive house prices).

South of the river, e.g. to Brixton, took a lot longer to arrive and the tunnel work was a lot harder with former rivers and earth more substantial than clay to get through.

So yes, anything is possible given money, however, geology still gets in the way.