No, not The Tube, London's subway system for which you always have to Mind The Gap.
To migrate from the Star Alliance Arrivals Lounge to the LHR Hilton, we first took the Heathrow Express, which offers a free ride to Terminal 4.
Once there, we took a lift up to the departure level and found the adjacent entrance to the Hilton's tube, a covered walkway that leads to the hotel.
We then went tubing.
And we kept on tubing, meeting nobody along the way but a solitary employee somewhere near the middle mopping the floor - that must be a full-time job.
Finally we emerged from the tube - about six minutes later as the sign at the entrance touted - to the great outdoors and a quick breath of fresh air before entering the hotel.
Our room is on the top floor, and the gangway-like open corridors from the lifts to the room hallways on each side offer a good view of the main floor in both directions.
We'll visit the Executive Lounge on the ground floor later, but now it's nap time.