Didn't an anon post a London bus route map last night? I remember seeing a route/red line drawn that reminds me of a line connecting these two points.
It was the "E" route…found the route map. Goes from Great Portland to Big Ben and Westminster. Can't format it to post here, but this is the link to the map itself
https:// tfl.gov.uk/maps/bus?Input=Great%20Portland%20Street%20Station&InputGeolocation=51.522971,-0.143923