Take him on a trip to Ashford kent on the high speed service ( 38mins from St Pancras). Fair bit goes on to keep him interested, splitting and joining trains,
Pantographs going up and down on the "Javelins", odd freight train if you're
there at the right time
and Eurostars going over the viaduct next to platform 6
Nice breakfast roll available at the cafe in the station entrance, or Maccy D at the
Outlet centre 5 min walk or courtacy bus
If he'd like a trip along the bottom of the White Cliffs by the sea have a trip to
Dover and back
If you're really lucky and there's plenty of time at St Panc and you're good at fluttering Eyelashes he might be able to look in the cab, depends on who the Driver is, on the whole they are a good lot
Hope this helps
Are we there yet