Here's how I did it:
Put embarrassment, coyness and thoughts of looking like a tourist to one side.
Put the camera on the floor of the Tube, directly in front of the seats opposite you.
Set the timer (I used the 9 second delay option), press the shutter and scurry back to your seat.
Pose your feet prettily.
This second image shows our first attempt.
It would appear that The Brainy One had left a leg in the West End.
Things to note:
This kind of shot works well when your Tube carriage is fairly empty.
When we use the Tube to come home from the West End, we travel to the end of the line.
I knew that I would have useable floor space eventually.
Indeed, it took the train pulling into our station before I could pull off this shot.
I still had to dodge the passengers getting on the train for the ride back into town
and a driver who had thought to leave the train through the carriage.
(We were sitting in the front carriage, directly behind the driver's compartment.)
He was a very understanding driver.
He's probably seen it all.