The next time you find yourself on the wrong side of Euston Road road for St Pancras station, take this underpass here: https://www.google.com/maps/@51.5302507,-0.1231112,3a,75y,25...
It does require local knowledge to expect this, I'll grant.
It seemed impossible to get to my hotel from the Eurostar train in a reasonable time with the tube when I came in on an after work train. Ended up with an unlicensed cab with a driver who spoke with a very deep cockney accent and dropped us off on the wrong side of the street where there was a fence to prevent pedestrian crossings. It was an adventure. I never ended up on the tube, because it was simpler to just walk to the office.