From Milngavie station where I live, which connects with Glasgow Central, where is the furthest place I can travel by rail without having to leave a rail or metro station? (My query is prompted by spending Monday morning trapped behind someone in the ticket office queue who seemed to be purchasing a season ticket to Kazakhstan.) David Henderson

Our immediate reaction was Ho Chi Minh City (formerly Saigon) in southern Vietnam; this assumes you take the train from Milngavie via Glasgow Central to London, thence via Brussels, Berlin, Moscow and Beijing (though as far as we know you cannot yet buy a ticket to Ho Chi Minh City from the booking office at Milngavie station). However, to make sure, we checked with Mark Smith, the Man in Seat Sixty-One. He pointed out a possible flaw caused by the Moscow Metro system, where underground stations do not always connect with main-line terminals.

"Saigon is probably the answer Mr Henderson is after – it thankfully still says 'Sai Gon' in the official Vietnamese timetables and on the station building itself," he says. "But I have a nagging feeling it might actually just be Moscow. That's because, as I recall, you have to emerge from the Metro station in the square opposite Yaroslavsky station, and cross the road to the station, thus invalidating the journey beyond Moscow by Mr Henderson's criterion! However, I dare say an ingenious route via Warsaw, Kiev, Kharkov, Irkutsk, Beijing might get around this."