Hop On Off Bus St Pancras

If you actually want to get from somewhere to St Pancras (or vice-versa), you would be better of using the tube or a normal bus. Hop on off buses are a lot more expensive than public transport, and slower.

I found three that cover St Pancras. They all have multiple routes (London is that big). So no one bus will cover all things to see and St Pancras.
1) https://www.theoriginaltour.com/ Route map: https://www.theoriginaltour.com/media/3177/tot_london_summer18_map_hires_160518.pdf
2) https://www.bigbustours.com/en/london/london-routes-and-tour-maps/
3) http://www.hoponhopoffplus.com/routes-and-maps

There may be more.

It is interesting about those offerings. In all my trips in and out of both St Pancras and Kings Cross (and of course Euston) I have never seen either a HoHo bus passing or a HoHo bus stop.

Of course I wasn't looking for one, but I would have noticed if I had seen one.

Guess they are there, just unobservant Nigel.

Yeah, they are there. Our hotel was just up the street from St Pancras, and I saw them several times. But I'd only use them for sight seeing, not for getting quickly to a specific destination. Regular buses or the tube are so much more efficient.

There are tourist buses that call at St Pancras - the stop on Midland Road near the northern entrance to the station, the one by the escalators down to Thameslink, but the route is quite infrequent.

If you actually want to get to St Pancras, and not start a tour there, use a different means of transport.